Incorporating Daoist Practices into Zen: Hakuin Ekaku’s Adaptation of Inner Alchemy and Its Cross-Cultural Impact

Abstract

Hakuin Ekaku 白隠慧鶴, the reviver of the Japanese Rinzai school 臨濟宗, introduced Chinese Daoist cosmology and views on the body through the narrative persona of the immortal Hakuyūshi 白幽子 in works such as Yasen Kanna 夜船閑話 (Chats on a Night Boat). He elaborated on specific techniques of Daoist internal alchemy (nèidān 內丹), such as focusing the mind on the dāntián 丹田 (elixir field) and regulating the breath to enter a state of tranquility, as methods to address “Zen sickness” and nurture both body and mind. This approach to self-cultivation exerted a profound influence in Japan. From the late Meiji into the Taishō period (early 20th century), practitioners such as Futaki Kenzo 二木謙三, Fujita Reisai 藤田靈齋, and Okada Torajirō 岡田虎二郎 developed their own health methods based on their respective understandings, forming practices such as the “abdominal breathing method” 腹式呼吸法 and the “method of harmonizing breath and mind” 息心調和法. These contributions promoted the popularization of quiet sitting within Japanese society. Related books were subsequently translated and introduced to China, inspiring modern scholars such as Jiang Weiqiao 蔣維喬 to reinterpret Chinese traditional self-cultivation methods in a new language, leading to the publication of health-preserving works like The Yinshizi’s Method of Quiet Sitting 因是子靜坐法. At the same time, the Chinese self-cultivation community engaged in reflection on and correction of potential drawbacks in the practice of sitting meditation. By tracing this cross-religious and cross-regional process of cultural transmission and transformation, this paper reveals the enduring vitality of Daoist practices during East Asia’s modernization, as well as their universal significance beyond the confines of any single religious tradition.

1. Introduction

Hakuin Ekaku 白隠慧鶴 (1685–1768) was a renowned monk, writer, and artist of the Edo period in Japan, later honored as the reviver of the Japanese Rinzai school 臨濟宗. Born into the Nagasawa family of Harajuku in Suruga Province (present-day Shizuoka Prefecture), his secular name was Iwajirō 岩次郎. From a young age, Iwajirō was erudite, talented, and demonstrated exceptional aptitude for scholarship and the arts. In the twelfth year of Genroku (1699), at the age of fifteen, Iwajirō was ordained as a monk under the priest Tōryō Soden 單嶺祖傳 at Shōinji Temple 松蔭寺 in his hometown, receiving the dharma name Ekaku. In the sixteenth year of Genroku (1703), Hakuin traveled to Zenshūji Temple 禪叢寺 in Shimizu Township 清水鄉, where he experienced a crisis of faith, developed doubts about the Buddhist teachings, and temporarily turned his focus to composing poetry and immersing himself in literary pursuits.

In the first year of Hōei (1704), he journeyed to Zuunji Temple 瑞雲寺 in Nōshū (present-day Gifu Prefecture), where he studied under the monk Maō 馬翁. Upon reading Changuan Cejin 禪關策進 (Breaking Through the Barriers of Zen Practice), compiled by the eminent Ming dynasty monk Yunqi Zhuhong 蓮池袾宏, Hakuin rekindled his faith in Buddhism and his desire to seek the truth. From then on, he dedicated himself to diligent and arduous Zen practice. In the fifth year of Hōei (1708), Hakuin arrived at Kōden Eganji Temple 高田英岩寺 in Echigo (present-day Niigata Prefecture). While listening to the monk Seitetsu 性徹 expound Rentian Yanmu 人天眼目 (The Eye of Humans and Gods), he was deeply moved. He engaged in intense investigation for over ten days, neither sleeping nor eating, until one night, upon hearing the temple bell ring, he experienced a transcendent and unprecedented state of being: his mind became clear, his true nature was revealed, and the six sense faculties (liùgēn 六根) no longer clung to externals, and the six sense objects (liùchén 六塵) dissolved. He believed he had attained enlightenment, and thus gave rise to self-conceit.

Later that same year, while visiting Dōkyō Etan 道鏡慧端 at Shōju-an Temple 正受庵 in Shinano (present-day Nagawa, Nagano Prefecture), Hakuin found himself unable to respond effectively during a dharma combat exchange. His self-conceit was instantly shattered, and he was once again plunged into uncertainty. As he was pondering this while wandering, an old woman suddenly chased him with a broom. In this abrupt and unexpected situation, Hakuin experienced a great and sudden enlightenment. Subsequently, he received Dharma transmission (Inka 印可) from Dōkyō and became his dharma heir. This marked the beginning of Hakuin’s post-enlightenment training and his life of traveling extensively to teach.

In the eleventh year of Kyōhō (1726), while reading the Lotus Sūtra one night, he realized its supreme status as the “king of kings” among sutras, suddenly merging with the Mahāyāna’s vast vows and wisdom. His years of doubt melted away, and he attained great liberation. In the fifth year of Meiwa (1768), Hakuin passed away peacefully at his home temple, Shōinji, at the age of eighty-four (Tōun 1963).

Since the Meiji era, Japan has witnessed a proliferation of writings on Hakuin, predominantly comprising popular readings or personal practice insights authored by monks or writers to promote his teachings. While abundant in content, these works largely emphasize introduction and popularization. In contrast, scholarly research that delves deeply into the distinctive characteristics of his thought and its historical significance remains relatively limited. Within academic circles, Tsukawa Taiun’s 陸川堆雲 Annotated Detailed Biography of Zen Master Hakuin 考證白隠禪師詳傳 stands as a pioneering work. Subsequently, the contributions of Katsuhiro Yoshizawa 芳澤勝弘 have been particularly outstanding. He not only presided over the compilation of the thirteen-volume Complete Collection of Zen Master Hakuin’s Kana Dharma Words 白隠禪師假名法語全集 and several other related treatises but also systematically advanced related research by establishing the “Hakuin Studies” 白隠學 column through the International Research Institute for Zen Studies at Hanazono University. Mr. Yoshizawa noted that the greatness of Zen Master Hakuin fundamentally lies in his practice-oriented approach of “seeking awakening Bodhi above and delivering all sentient beings below” 上求菩提，下化眾生. He argued that this unfinished mission requires reinterpretation and exploration in every era, and that a profound grasp of Hakuin’s thought necessitates transcending the traditional research frameworks of Buddhist history or Zen history (Yoshizawa 2022).

Hakuin was thoroughly versed in the teachings of Confucianism, Buddhism, Daoism, and other schools, with profound mastery of Classical Chinese. Beyond his dedication to propagating orthodox Zen, he excelled at employing diverse methods to guide people and benefit society. For instance, he drew upon Daoist health-preservation techniques to address Zen sickness among Zen practitioners. He disseminated these methods widely through literature, calligraphy, and painting, presenting them in vivid and accessible forms that ultimately benefited ordinary people. This article contends that Hakuin’s practice of “incorporating Daoist practices into Zen” precisely embodies the crucial implementation of his grand vow to “deliver all sentient beings below”.

The original texts embodying Hakuin’s concept of “incorporating Daoist practices into Zen” have been digitized, collated, and published in Japanese academia, laying an important foundation for subsequent research. However, due to differences in the cultural contexts of China and Japan, and the esoteric nature of Daoist internal alchemy, Japanese scholars still have room for exploration in understanding and interpreting the specific content and deeper logic of Hakuin’s citation of Daoist internal alchemy. Meanwhile, Chinese scholars have paid insufficient attention to this issue involving Daoism outside of China. Accordingly, this study aims to clarify two main questions. First, what specific theories and methods of Daoist inner alchemy did Hakuin Ekaku adopt, and how did he adapt and integrate them into his Zen cultivation system? Second, how did this distinctive practice of “incorporating Daoist practices into Zen” subsequently evolve into popular health methods in Japan, then flow back to China, and finally stimulate Chinese scholars to reinterpret their own traditions? To answer both questions, a unified research method is essential: meticulous textual investigation, terminological comparison, and conceptual analysis of Hakuin’s writings against key Daoist and Buddhist source texts, in order to accurately distinguish the origins and composition of his thought and practice. This analysis must also consider the historical context of Buddhist–Daoist intellectual interaction. From the earliest translation of Buddhist scriptures into Chinese, translators used Daoist terminology to explain Buddhist concepts. This established a shared conceptual foundation that later allowed for practical exchanges between the two traditions. Such mutual influence was especially clear in the development of Chinese Zen Buddhism. As Zen took root in China, it absorbed not only Daoist terms but also engaged with Daoist ideas on nature, mind, and spiritual practice (Funayama 2022; Z. Li 2023). Later, Daoist internal alchemy likewise integrated key Zen insights—such as the emphasis on “seeing one’s true nature” (jiànxìng 見性)—into its own framework (Fang 1995; Qi 2024). Against this long background of cross-tradition interaction, the Japanese Zen master Hakuin’s incorporation of Daoist inner-alchemy methods represents a distinctive and historically grounded example. By examining his work closely, this study seeks to clarify both the specific content of his synthesis and the broader capacity of such practical knowledge to cross religious boundaries and be continuously recreated.

2. The Theoretical Construction and Practical Path of Hakuin’s “Incorporating Daoist Practices into Zen”

To broaden the dissemination and acceptance of his teachings, Zen Master Hakuin employed a variety of literary styles in his writings. His works include recorded sayings composed entirely in Classical Chinese, such as Kanzanshi Sendai Kibun 寒山詩闡提記聞, Hebyōsō 壁生草, and Kaian Kokugo 槐安國語; Japanese literary texts that maintain Classical Chinese phrasing, such as Yasen Kanna 夜船閑話 and Orategama 遠羅天釜; as well as Dharma words and short songs written in kana with a tale-like style. In terms of narrative style, Hakuin often adopted an autobiographical approach, using his own experiences as teaching examples to enhance the textual impact and pedagogical effectiveness. Yasen Kanna is a typical example. This work, written in kana while preserving Classical Chinese phrasing, recounts the story of Hakuin, while ill, encountering the immortal Hakuyūshi 白幽子 and receiving from him secret health-preservation techniques, thereby restoring his health. This narrative also appears in Orategama, Kanzanshi Sendai Kibun, and Hebyōsō, with largely consistent content. Collectively, these texts form the primary basis for our analysis of his thought regarding the incorporation of Daoist practices into Zen.

In terms of content structure, the section in Yasen Kanna where Hakuyūshi expounds the methods of health preservation occupies significant space. Examining its content reveals that it in fact draws upon classics from Buddhism, Traditional Chinese Medicine, and Daoism, combined with Hakuin’s own insights. It is not difficult to conclude that Hakuin used the figure of Hakuyūshi as a mouthpiece to introduce to the general public the principles and specific practices of health cultivation. Hakuin’s authorial intent was fundamentally focused on resolving the physical and mental problems faced by both monastics and laypeople in their actual Zen practice, embodying his great vow to “deliver all sentient beings below”. Hakuin also directly stated the purpose of his writings:

The secret of vipassanā I wrote down thoroughly in Yasen Kanna previously for the sake of itinerant monks seeking the profound. I have constantly used these principles to save monks from Zen sickness; I do not know how many times. Among them, I have cured eight or nine out of ten who faced severe, certainly fatal illnesses. Scholars must surely combine and store up vipassanā together with Zen inquiry, and thereby accomplish the fundamental aspiration of their lives. 內觀ノ秘訣ハ予向キニ江湖參玄ノ衲子ノ爲メニ夜船閑話ニ書シ了レリ。予常ニ此等ノ趣キヲ以テ衲子ノ禪病ヲ救フ事幾許ト云フ數ヲ知ラズ、中ニ就イテ重症必死ニ向トスル者八九ヲ治ス。學者必ズ內觀ト參學ト共ニ合セ並ベ貯ヘテ以テ生平ノ本志ヲ成ゼヨ。

(Hakuin 2001, pp. 245–46)

The “Zen sickness” 禪病 referred to by Hakuin denotes a range of physiological and psychological disorders arising from improper methods or psycho-physical imbalances during seated meditation, which in severe cases could be life-threatening. This predicament of practice had long been a concern within the Buddhist tradition, as evidenced by the systematic discussion of its categories and treatments in the Scripture on the Secret Essentials for Curing Zen Sickness 治禪病秘要經, translated during the Liu-Song dynasty. In traditional Chinese cosmology, such disorders were ultimately attributed to a disruption in the circulation of vital energies within the body, contravening the natural order. Daoism developed particularly astute observations and methods for diagnosing and rectifying such imbalances, and this corpus of knowledge was consequently borrowed and adapted within Buddhist cultivation. When the Sui dynasty monk Zhiyi 智顗 (538–597) elaborated various therapeutic methods for Zen sickness in his Mohe Zhiguan 摩訶止觀 (The Great Cessation and Contemplation), his exposition likewise demonstrated an assimilation of such Daoist-informed knowledge (Xiao 2000). This tradition of Buddhist–Daoist interaction, grounded in pragmatic necessity, appears to have persisted. It is said that in hermitages such as those on Zhōngnán Mountain 終南山, the practice of monks and Daoists living in close proximity continues, partly because Daoist adepts are traditionally considered skilled at treating Zen sickness. While anecdotal, this modern observation offers a tangible vignette of the historical exchanges underpinning such syncretic practices. Hakuin’s lament that he saved monks from Zen sickness “I do not know how many times” attests to its distressing prevalence within his community. This reality compelled him to turn to and incorporate elements from Daoist practice. However, since Daoism and traditional Chinese medicine share fundamental cosmological and physiological principles, what Hakuin introduced through the figure of Hakuyūshi pertains not solely to sectarian Daoist cultivation but to the broader field of Chinese medical and life-nourishing thought. To maintain analytical focus, the following discussion will primarily follow Hakuin’s own explicit framing and analyze his approach through the specific lens of Daoist internal alchemy (nèidān 內丹). Within the story, Zen Master Hakuin refers to Hakuyūshi as a “Daoist priest” (dàoshi 道士) and an “immortal” (xiānrén 仙人), and calls the vipassanā methods he teaches “internal alchemy”. These expressions are all concepts unique to Chinese Daoism.

Daoism, as Chinese indigenous religion, together with Confucianism and Buddhism, forms one of the three pillars of traditional Chinese culture. Daoist practitioners take the “Dao” 道 as their ultimate destination, and the state of life that returns to the Dao is called that of an “immortal”. One of the core means to achieve this goal is internal alchemy. The term “internal alchemy” borrows terminology from external alchemy (wàidān 外丹), but in reality, it has little connection with a tangible pill. Its theoretical foundation lies in the Daoist cosmological view of “correspondence between heaven and humanity” (tiānrén tónggòu 天人同構), which posits that the human body is a microcosm, possessing the same energy sources, structure, and operational principles as the external universe. Therefore, one does not require external elixirs; through internal cultivation, the sublimation of life can be achieved, ultimately leading to union with the Dao. Thus, the process is likened to forging an imperishable golden elixir within the body, which is why it is called “internal alchemy”. The theoretical system of internal alchemy is profound and its content rich. The following analysis will focus specifically on the relevant content cited by Hakuin in texts such as Yasen Kanna.

2.1. Elucidating the Health-Preservation Principles of Daoism

The practice of internal alchemy must be founded upon an understanding of fundamental Daoist concepts, such as its cosmology and view of life. In Yasen Kanna, Hakuin introduces these relevant concepts by constructing the narrative of Hakuyūshi diagnosing his illness. Hakuin recounts that even after his enlightenment, he diligently practiced Zen meditation, even to the neglect of food and sleep. Several months later, however, he contracted a strange illness. Its symptoms were described as follows: “My feet feel as if they are immersed in ice and snow, my ears feel as if they are listening to the sound of a stream, I am often terrified and mentally exhausted, I see all sorts of visions in my waking and sleeping, my armpits are often sweaty and my eyes are often filled with tears.” (Hakuin 2000, pp. 99–100). Although Hakuin sought treatment from numerous physicians, none proved effective. Later, following a villager’s guidance, he ventured deep into the mountains and found the immortal Hakuyūshi in a rocky cave. Using the Traditional Chinese Medicine method of pulse diagnosis, Hakuyūshi examined him and identified his condition as “Zen sickness”. He attributed the root cause to “excessive contemplation and improper practice” 觀理過度，進修失節, and further elaborated on the rationale as follows:

The Great Dao divides into the Two Modalities; through the interaction and harmony of Yin 陰 and Yang 陽, human beings and all things are born. The innate Yuán Qi元氣 (vital Qi; vital energy) operates silently: the five zang-organs (wǔzàng 五臟) are positioned, the meridians flow, and the Defensive Qi (wèiqì 衛氣) and Nutritive Blood (yíngxuè 營血) circulate fifty times during each day and night. The Lungs Metal, float above the diaphragm; the Liver Wood, sinks below it. The Heart Fire and being the Greater Yang, resides above; the Kidneys Water and being the Greater Yin, reside below. The five zang-organs store the seven Spirits (shén 神), with the spleen and kidneys each storing two. 夫れ大道分れて兩儀あり。陰陽交和して人物生る。先天の元氣、中間に默運して、五臟列り、經脈行わる。衛氣營血、互に昇降循環する者、晝夜に大凡五十度。肺金は牝臟にして膈上に浮び、肝木は牡臟にして膈下に沈む。心火は大陽にして上部に位し、腎水は大陰にして下部を占む。五臟に七神あり、脾腎各々二神を藏す。

(Hakuin 2000, pp. 110–13)

This passage centrally expounds the core Daoist views on the origin of life and the operational principles of the human body. Its theoretical sources can be traced back to classics such as the Laozi 老子 and the Nan Jing 難經. The first sentence points out that all things are born from the Dao. Two Modalities (liǎngyí 兩儀) refers to a pair of basic categories that are differentiated from the unified Dao—Yin and Yang. The two are both opposed and unified, interdependent and mutually fundamental. This concept originates from the Laozi (Chapter 42), which states: “The Dao generates the One; the One generates the Two; the Two produce the Three; the Three produce the myriad things. The myriad things carry Yin and embrace Yang, and through the mediation of Chōng Qi, they achieve harmony.” 道生一，一生二，二生三，三生萬物。萬物負陰而抱陽，沖氣以為和。 (Laozi 2014, pp. 165–66). Daoist philosophy emphasizes the fundamental role of Qi 氣 in the constitution of the cosmos and the activities of life, regarding it as the essential element sustaining life, hence the saying, “With qi there is life; losing qi leads to death.” 有氣則生，無氣則死 (Xiangfeng Li 2004, p. 214). Qi is the fundamental vital force or life-energy in Chinese thought, medicine and spiritual practice. It is the dynamic substrate that animates the body, drives physiological functions, and connects the individual to the cosmos. Similar concepts of subtle life-force found across cultures include Prana (Yoga/Ayurveda), Pneuma (Ancient Greek), and Mana (Polynesian). Later Daoist scholars often interpreted Laozi’s aforementioned words from the perspective of the transformation of qi. For example, Zhang Boduan 張伯端, founder of the Southern School of Daoism 道教南宗, stated in his Wuzhen Pian 悟真篇 (Awakening to Reality): “The Dao, from Emptiness and Nothingness, generates the One Qi; then from the One Qi emerge Yin and Yang. Yin and Yang, combining again, generate the Three Forms; the rebirth of the Three Forms leads to the flourishing of the myriad things.” 道自虛無生一氣，便從一氣產陰陽。陰陽再合生三體，三體重生萬物昌。 (B. Zhang 2015, p. 63). Here, the Dao as the ultimate origin is absolute, formless, and unnameable, hence “Emptiness and Nothingness” (xūwú 虛無) is used to symbolize its essence. The production of the One Qi (yīqì 一氣) symbolizes the initial state where the Dao’s substance begins to function and the myriad things are about to sprout. This One Qi further divides into the two poles of Yin Qi 陰氣 and Yang Qi 陽氣, indicating the transition from undifferentiated unity to relative distinction, from which the myriad things of the finite world are generated. The interaction and fusion of the Yin Qi and Yang Qi produce the Chōng Qi 沖氣. All things receive this harmonious energy to complete their life.

As the Chōng Qi constitutes the foundation of individual life, it is also termed Yuán Qi in many texts. For instance, the Laozi Heshang Gong Zhangju 老子河上公章句 states: “Within the myriad things, all possess innate Yuán Qi, which enables them to be harmonious and soft… thus they can endure long.” 萬物中皆有元氣，得以和柔……故得久生也。 (Wang 1993, p. 169). This excerpt from Yasen Kanna is a concrete description of how Yuán Qi forms and sustains human life.

The five zang-organs and meridians (Jīngluò 經絡) are the most vital components of the human body, with their attributes and functional principles adhering to the doctrines of Yin-Yang 陰陽 and the Five Phases (Wǔxíng 五行). Each zang-organ corresponds to one of the Five Phases: the Liver to Wood (mù 木), the Heart to Fire (huǒ火), the Spleen to Earth (tǔ 土), the Lung to Metal (jīn 金), and the Kidney to Water (shuǐ 水). Furthermore, these organs maintain specific Yin-Yang relationships among themselves. For instance, both the Heart and Liver pertain to Yang, while the Spleen, Lung, and Kidney belong to Yin. Between the Heart and the Liver, the Heart embodies a more predominant Yang quality, thus designated as “Greater Yang” (tàiyáng 太陽); similarly, the Kidney is referred to as “Greater Yin” (tàiyīn 太陰). It is essential to emphasize that the terms “Heart” (xīn 心), “Liver” (gān 肝), “Spleen” (pí 脾), “Lung” (fèi 肺), and “Kidney” (shèn 腎) in traditional Chinese medical texts should not be simplistically equated with discrete anatomical organs in the modern sense. Rather, they represent a dynamic and interactive energy system. Traditional Chinese thinking often transcends the tangible, physical level, comprehending the vital activities of the human body through the framework of flowing qi. This perspective allows for a grasp of the characteristics of various functional systems and their intricate connections with the whole. Consequently, in numerous classical texts, the “Heart” is often conceptually merged with or expressed as “heart-qi” (xīnqì 心氣) or “heart-fire” (xīnhuǒ 心火).

According to Daoist theory, the qi of the five zang-organs mutually generates, promotes, and yet also restrains one another, collectively maintaining the health of the human body. The meridians are the vital pathways that connect the zang-organs and other tissues. Qi, as the foundation of life, is primarily produced and transformed by the zang-fu organs 臟腑, and it circulates, interacts, and distributes throughout the body along the meridians. Starting from its second sentence, the quoted passage elaborates on this very mechanism, placing particular emphasis on the key activity for sustaining postnatal life—respiration. Respiration is a result of the synergistic participation of the zang-organs and meridians, enabling the circulation and rhythmic exchange of qi within the body and the qi of the natural world.

From a functional perspective, the normal operation of sensory and conscious activities relies on the coordinated propulsion of the qi of the zang-organs. For instance, “Liver-qi connects with the eyes; when the Liver is harmonious, the eyes can distinguish the five colors.” 肝氣通於目，目和則知白黑矣。 (Sima 1982, p. 2820). The zang-organ most closely related to conscious activity is the Heart. Traditional Chinese Medicine adheres to the doctrine that “the spirit resides in the heart, and all emotions and desires are governed by the heart”. 神藏於心，而凡情志之屬，惟心所統。 (Jiebin Zhang 2016, pp. 58–59). This posits that the Heart governs a person’s mental and emotional faculties. Consequently, the excessive use of the senses and consciousness can, in turn, disturb the qi of the zang-fu organs and even disrupt the functional balance among the five zang-organs, ultimately resulting in the manifestation of various refractory diseases.

In the quotation, Hakuin particularly emphasizes that among the five zang-organs, the interaction between Heart (Fire) and Kidney (Water) is especially important, forming a primary Yin-Yang relationship within the body. In a healthy human body, the Heart-Yang, residing above the diaphragm, descends to warm the Kidney-Yin, preventing it from becoming too cold; while the Kidney-Yin, residing below, ascends to moisten the Heart-Yang, preventing it from becoming hyperactive. This brings the human body to a “cool above, warm below” state. This dynamic balance is called “the interaction of the heart and kidneys” (xīnshèn xiāngjiāo 心腎相交), which corresponds to the “water and fire in harmony” (shuǐhuǒ jìjì 水火既濟) hexagram in Zhouyi 周易 (the Book of Changes). This physiological phenomenon relies on the True Yin (zhēnyīn 真陰) within the Heart and the True Yang (zhēnyáng 真陽) within the Kidneys as internal motive forces, with other organs and meridians cooperatively participating to accomplish it (Sun 1982). However, according to the Five Phase attributes, Fire’s nature is inherently to rise. If a person contemplates excessively, it is like adding too much fuel to the Heart-fire, easily leading to excessive Heart-Fire that cannot descend. Thereby, the state of Heart–Kidney interaction is disrupted. Furthermore, according to the Five Phase controlling cycle, Fire controls Metal 火克金; hyperactive Heart Fire will directly damage the Lungs, which also reside above and belong to Metal. And because Metal generates Water 金生水, damaged Lung-Metal finds it difficult to nourish and produce the Kidneys-Water, thereby triggering a chain reaction of dysfunction in the five zang-organs, ultimately leading to the emergence of numerous diseases. This explains Hakuin’s affliction with sickness. In Yasen Kanna, Hakuyūshi explicitly stated:

Sir, your grave illness stems from the adverse rising of heart-fire. Unless this fire is redirected downward, even the most profound methods from all three realms will prove ineffective. Do not assume that my approach deviates from the Buddha’s teachings merely because my outward form resembles that of a Daoist. Regarding the contemplation of principles, one must regard non-contemplation as correct, and excessive contemplation as erroneous. You have fallen ill due to excessive contemplation; now, you can only be saved through non-contemplation. Direct the heart-fire into the dāntián and the soles of the feet, thereby achieve a state of cool clarity in the chest and diaphragm, free from the waves of discriminative thought, that is what is called “True Contemplation and Pure Contemplation”. 公先に心火逆上して此の重痾を發す。若し心を降下せずんば、縱ひ三界の秘密を行じ盡したりとも、起つ事得じ。且つ又我が形模、道家者流に類するを以て、大に釋に異なる者とするか。是禪なり。他日打發せば大に笑ひつべきの事有らむ。夫れ觀は無觀を以て正觀とす。多觀の者を邪觀とす。向きに公、多觀を以て此の重症を見る。今是れを救ふに無觀を以てす。また可ならずや。公若し心炎意火を收めて丹田及び足心の間におかば、胸膈自然に清涼にして一點の計較思想なく、一滴の識浪情波なけん。是れ真觀清靜觀なり。

(Hakuin 2000, pp. 129–30)

The quoted passage presents the essential healing principle of “directing the heart-fire into the dāntián and the soles of the feet”. This formulation is repeatedly emphasized within Yasen Kanna, sometimes specified more concretely as “directing the heart-fire down to the Sacral Chakra (qílún 臍輪), the Sea of Qi (qìhǎi 氣海), the dāntián, the waist and legs, and the soles of the feet”. 降心火於臍輪、氣海、丹田、腰、腳、足心。From the perspective of Chinese medical meridian theory, these locations are all key areas traversed by the Kidney Meridian. Directing the heart-fire to these regions reflects the aforementioned traditional health preservation logic of achieving “the interaction of the Heart and Kidneys” and “water and fire in harmony”. How, then, should this essential health principle be concretely practiced? This question leads directly to the specific content of how Hakuin integrated Daoist internal cultivation techniques, which will be analyzed in the following section.

2.2. Adopting the Foundational Methods of Internal Alchemy: Guarding the One and Regulating the Breath

Based on the Daoist cosmological and mind–body concepts discussed previously, Hakuin establishes in Yasen Kanna the core cultivation principle of directing the heart-fire downward. To further demonstrate its feasibility and clarify its specific practical methods, he subsequently references both Buddhist and Daoist literature, which will be examined in the following three aspects.

2.2.1. Citing the Mohe Zhiguan to Establish the Practice of Focusing the Mind on the Dāntián

In Yasen Kanna, Hakuin establishes his method by citing from the Buddhist text Mohe Zhiguan, as illustrated in the following passage:

The Buddha said: “Place the mind at the soles of the feet to cure the hundred diseases.” The Āgamas contain a method using ghee, which is especially effective for relieving mental fatigue. The Mohe Zhiguan of the Tiantai school 天台宗 discusses the causes of illness and their treatments with precision and detail, including the twelve kinds of breath that cure various illnesses, and the method of contemplating a bean-sized object at the sacral chakra. These methods direct the heart-fire down to the dāntián and the soles of the feet, not only treating illness but also aiding Zen contemplation. Among the two types of cessation-and-contemplation (zhǐguān 止觀): Xìyuán 繫緣 (object-anchoring) and Dìzhēn 諦真 (truth-contemplation). Dizhen is the holistic observation of true reality, while Xiyuan is primarily concerned with directing the heart-fire down to the Sacral Chakra, the Sea of Qi, the dāntián. 佛の言く、心を足心におさめて、能く百一の病を治すと。阿含に酥を用ゆるの法あり。心の勞疲を救ふ事尤も妙なり。天台の摩訶止觀に病因を論ずる事甚だ盡せり。治法を說く事も亦甚だ精密なり。十二種の息あり、よく眾病を治す。臍輪を縁して豆子を見るの法あり。其の大意、心火を下降して丹田及び足心に收むるを以て至要とす。但病を治するのみにあらず、大に禪觀を助く。蓋し繫緣諦真の二止あり。諦真は實相の圓觀、繫緣は心氣を臍輪氣海丹田の間に收め守るを以て第一とす。

(Hakuin 2000, pp. 131–33)

The “method of contemplating a bean-sized object at the sacral chakra” mentioned corresponds to the following original text: “Master Wen said: ‘Fasten the mind in the navel, on a spot the size of a bean. Loosen your clothing, observe the appearance attentively and grasp the mental image. Afterwards, close the eyes, bring the lips and teeth together, raise the tongue against the palate, and make the breath regulated and even. If the mind runs outward, gather it and make it return. If you cannot retain the image, loosen your clothing again and look at the navel, familiarize yourself with the appearance, grasp it, and then proceed as before.’” This passage comes from Volume Eight of the Mohe Zhiguan. This volume also records a method of healing by focusing the mind on the dāntián: “The dāntián is the Sea of Qi, capable of ‘locking’ and ‘swallowing’ the ten thousand illnesses. If one settles the mind at the dāntián, then the breath become harmonized, and therefore it can cure disease.” The saying in the Yasen Kanna quotation, “The Buddha said…” is also found in the same volume (Zhiyi 1987, p. 204). Clearly, this understanding shares similarities with the aforementioned Daoist viewpoints. The Mohe Zhiguan is considered to have borrowed and absorbed some elements of Daoist culture. Its eighth volume lists six methods for overcoming difficulties in meditation: “1. Zhǐ 止, 2. Qì 氣, 3. Xī 息, 4. Jiǎxiǎng 假想, 5. Guānxīn 觀心, 6. Fāngshù 方術,” some of which are similar to traditional Daoist health cultivation methods. The methods introduced above all fall under the category of Zhǐ (stopping), which is highly similar to the Daoist practice of Guarding the One (shǒuyī 守一). Hakuin believed that this could achieve the effect of lowering the heart-fire, and for this reason, he specifically emphasized in Orategama:

The gist of this section on the Mohe Zhiguan is this: Regardless of how much one studies the sacred teachings or contemplates the Dharma principles, or whether one sits long hours without lying down or practices the teachings of the Buddha throughout the day and night, if one can constantly keep the heart-qi directing down to the Sacral Chakra, the Sea of Qi, the dāntián, the waist, and the feet, then even amidst bustling worldly affairs or at gatherings with guests, without a moment’s negligence, the Yuán Qi will naturally fill the dāntián. The area below the navel becomes warm and substantial, like a new inflated leather ball, full and vibrant. 書中ノ大意ハ、縱イ何ニ分ノ聖教ヲ披覽シ、何ニ分ノ法理ヲ觀察シ、或イハ長坐不臥シ、或ハ六時行導スト云ヘドモ、常ニ心氣ヲシテ臍輪氣海丹田腰腳ノ間ニ充シメ滿、塵務繁絮ノ間、賓客揖讓ノ席ニ於イテモ、片時モ放退セザル時キハ、元氣自然ニ丹田ノ間ニ充實シテ、臍下瓠然タル事ト、未ダ篠打チセザル鞠ノ如シ。

(Hakuin 2001, p. 190)

Notably, Hakuin particularly highlighted a causal relationship—he emphasized that by guiding the heart-qi, one can cause the Yuán Qi to naturally fill the dāntián. How should this viewpoint be understood? It fundamentally involves Hakuin’s integration of the Daoist view of life with its actual cultivation practices. The following analysis will unfold step by step.

2.2.2. Assimilating the Daoist View of the Sea of Qi, Dāntián, and Yuán Qi

To answer this, we must first examine the concepts of the dāntián, which provide the foundational rationale for this causal relationship. As Hakuin once elaborated in his Yasen Kanna:

There are three designated areas known as the “dāntián” within the human body. The one I refer to specifically is the lower dāntián. Both the Sea of Qi and the lower dāntián are located below the navel; in essence, they represent one entity bearing two names. The Sea of Qi is the precious repository for gathering and nurturing the Yuán Qi; the dāntián is the fortified citadel where the elixir is refined and longevity is preserved. An ancient saying expresses this principle: “The reason why rivers and seas can be kings over all the valley streams is because they excel at staying below them.” Since the vast ocean resides beneath all other waters, it can contain and receive all tributaries without increasing or decreasing. Similarly, because the Sea of Qi resides below the five zang-organs, it can gather and absorb the Zhēn Qi eternally without ever overflowing, ultimately enabling the accomplishment of the Spiritual Elixir and entry into the realm of the Immortals. 丹田ナル者ノ一身三處、吾ガ謂ユル丹田ハ、下丹田ナル者ナリ。氣海丹田各各臍下モ居ス。一實ニシテ二名在ルガ如シ。人ニ氣海丹田アリ。氣海ハ元氣ヲ收メ養フノ寶處。丹田ハ神丹ヲ精錬シ、壽算を保護スルノ城府ナリ。古云ク、江海所以能為百谷王者，以其善下之ト。滄海既ニ萬水ノ下ヲ占メテ、百川ヲ含容シテ增減ナシ。氣海既ニ五內ノ下ニ居シテ真氣ヲ収メテ飽ク事ナシ、終ニ神丹ヲ成就シ仙都ニ入ル。

(Hakuin 2001, p. 223)

Both the dāntián and the Sea of Qi originate from Daoist observation of specific loci within the human body. The Sea of Qi is regarded as the central hub where Yuán Qi converges, generates, and distributes—much like the ocean receiving countless rivers—serving as the “repository” of vital energy. The term “dāntián” 丹田 (elixir field), by analogy with the refining of external alchemy (wàidān 外丹), refers to the internal “field” where the Golden Elixir (jīndān 金丹) is cultivated. The “dāntián” referred to by Zen Master Hakuin in his Yasen Kanna and the previously cited Mohe Zhiguan specifically denotes the lower dāntián, which is essentially the same as the Sea of Qi. The foregoing definitions are inherited from Daoist classics, as illustrated by the following textual evidence:

Master Lü said: The reason why rivers and seas can be kings over all the valley streams is that they are humble and stay low, empty and receptive, acting through non-action, and thus all the streams come to them naturally. Viewed from this, the virtue of humility and lowering is great indeed. In the human body, the lower dāntián below the navel is the Sea of Qi. It is the root of the vital energy of the five zang-organs and six fu-organs, the source of the thirteen thousand five hundred breaths per day and night, and the ancestor of the twelve primary channels. If a person can diligently guard the lower dāntián, the Sea of Qi, guarding it without interruption, then the qi of all parts of the body will naturally gather towards it. 呂氏曰：江海之王百谷者，謙卑處下，虛以待之，無為為求，而百川自然來也。由此觀之，卑損之為道也大矣，人身以臍間下丹田為氣海，乃五臟六腑生氣之本，一萬三千五百息之源，十二經脈之祖，人能謹守下丹田氣海，守之不間，則百關之氣自然朝之。

(Wei 1988, p. 616)

Three inches below the navel is the Sea of Qi, also called the lower dāntián, and also called the Xuán-Pìn 玄牝 (Mysterious Female). Ordinary people often mistake the mouth and nose for the Xuan-Pin, but this is incorrect. The mouth and nose are merely the gates through which the Xuan-Pin exits and enters. Now, Xuan 玄 refers to water, and Pìn 牝 refers to mother. People are born through the interaction of the Yin Qi and Yang Qi, which congeal within the water-mother. After three months, the embryo is formed; after ten months, the physical form is complete, and it can give birth to a person. Cultivators of the Dao constantly subdue their Qi below the navel and guard their Spirit within the body. When the Spirit and Qi unite, they generate the mysterious embryo (xuántái 玄胎). Once the mysterious embryo is formed, it naturally generates a spiritual body. This constitutes the internal elixir, the way of immortality. 臍下三寸為氣海，亦為下丹田，亦為玄牝。世人多以口鼻為玄牝，非也。口鼻即玄牝出入之門。蓋玄者水也，牝者母也。世人以陰陽氣相感，結於水母，三月胎結，十月形體具而能生人。修道者，常伏其炁於臍下，守其神於身內，神炁相合而生玄胎，玄胎既結，乃自生身，即為內丹，不死之道也。

(Huanzhen 1988, p. 868)

The first passage is excerpted from the Collected Commentaries on the Dao De Zhenjing 道德真经集義, compiled by Wei Dayou 危大有 of the Ming 明 dynasty, and presents the commentary by the Song dynasty Daoist Lü Zhichang 呂知常 on Chapter 66 of the Laozi. The line, “The reason why rivers and seas…” is a direct quotation from Laozi, frequently cited by later Daoist scholars in the context of the body to illustrate the Sea of Qi within the human body. As discussed earlier, Laozi pointed out that all things are born through the Chōng Qi. Daoism inherited this concept and further specified that the place in the human body where this Chōng Qi is initially received is precisely the Sea of Qi. As stated in Yunji Qiqian 雲笈七籖, Juan 58: “The Sea of Qi is where one first receives qi and where physical form begins its transmission; it is located three inches below the navel.” 氣海者是受氣之初，傳形之始，當臍下三寸是也。 (Junfang Zhang 1988, p. 406). The second passage, which offers a more detailed exposition on this topic, is attributed to Master Huanzhen’s 幻真先生 Commentary on the Classic of Fetal Breathing 胎息經. In both texts, the Sea of Qi is regarded as the root of life and natural transformation. During the fetal stage in the womb, before mouth and nose breathing commence, the Yuán Qi is wholly concentrated in the area below the navel. After birth, as breathing shifts to the postnatal pattern, the Yuán Qi begins to be utilized. Coupled with the gradual increase in the seven emotions and six desires (qīqíng liùyù 七情六慾), the Yuán Qi is gradually depleted as the Spirit moves outward, leading the individual toward aging and death. Therefore, Daoist practitioners strive to withdraw sensory engagement, reduce the external expenditure and dissipation of Yuán Qi, and further seek to continuously refine, consolidate, and nurture Yuán Qi at the dāntián and Sea of Qi. Their aim is to prolong life and ultimately attain transcendence. This constitutes the theoretical foundation for Zen Master Hakuin’s emphasis on the Sea of Qi.

2.2.3. Introducing Daoist Fetal Breathing Method

Based on the aforementioned goal of protecting Yuán Qi, Daoism developed various cultivation methods, which can be broadly divided into two orientations: The first is “Guarding the One”, which involves concentrating the mind on a single point to protect the spirit, consolidate vital energy, maintain life, and return to the origin. The various methods in the aforementioned Mohe Zhiguan can be considered part of this category. The second orientation is the “Fetal Breathing Method” (tāixī fǎ 胎息法). This involves regulating the breath to pursue a state where mouth and nose breathing seem to exist yet not exist, as if in the womb—simulating the fetal respiratory state in the mother’s abdomen, thereby returning to the primordial state of abundant Yuán Qi. The previously cited Classic of Fetal Breathing is a typical representative of this method. In Yasen Kanna, after introducing the cessation methods from the Mohe Zhiguan, Zen Master Hakuin cites two passages on fetal breathing techniques. The texts are as follows:

This is precisely what the Su Wen means when it states: “When one is tranquil and empty, the Zhēn Qi follows; when the spirit is guarded within, from where can illness arise?” The essential point of “guarding within” is to allow the Yuán Qi to fill the entire body—permeating all three hundred and sixty joints and eighty-four thousand pores—so that not a single fragment is lacking. Peng Zu said: Harmonize the spirit and guide the qi, in a closed quiet room, on a warm mat, pillow two and a half inches high, lie on your back closing the eyes, hold the qi in the chest and diaphragm, place a goose down on the nose unmoving, through three hundred breaths, the ears hear nothing, the eyes see nothing, cold, heat, bees, and scorpions cannot invade, lifespan three hundred sixty years, nearing the Zhēnrén (the Perfected Person). 是れ蓋し『素問』に謂ゆる恬澹虛無なれば、真氣これにしたがふ、精神内に守らば、病何れより來らんといふ語に本づき玉ふものならむか。且つ夫れ内に守るの要、元氣をして一身の中に充塞せしめ、三百六十の骨節、八萬四千の毛竅、一毫髮ばかりも欠缺の處なからしめん事を要す。是れ生を養ふ至要なる事を知るべし。彭祖が曰く、和神導氣の法、當に深く密室を鎖し、牀を安じ、席を煖め、枕の高さ二寸半、正身偃臥し、瞑目して、心氣を胸膈の中に閉し、鴻毛を鼻上につけて動かざる事三百息を經て、耳聞く處なく、目見る所なく、斯の如くなる則は寒暑も侵す事能はず、蜂蠆も毒する事能はず、壽三百六十歳、是れ真人に近しと。 Su Neihan said: When you feel slightly hungry but haven’t eaten enough, stop eating, walk until your stomach is empty, sit upright in a quiet room and silently count your breaths, from one to ten, from ten to one hundred, from one hundred to one thousand. Suddenly, you will feel your body become still and your mind become tranquil, as if you have merged with the void. Suddenly, you will feel your breathing through your mouth and nose seem to stop, and mist will rise from your eighty-four thousand pores. You will then realize that all the illnesses and obstacles from beginningless time have naturally disappeared, just like a blind person opening their eyes. At this time, there is no need to seek someone to point the way; you only need to omit ordinary words and nourish your Yuán Qi. As the saying goes: To nourish your eyesight, keep your eyes closed; to nourish your ears, keep them still; to nourish your heart, keep your mind silent. 又蘇内翰が曰く、已に飢えて、方に食し未だ飽かずして、先づ止む。散步逍遙して、務めて腹をして空しからしめ、腹の空なる時に當つて、即ち靜室に入り、端坐默然して出入の息を數へよ。一息より数へて十に到り、十より数へて百に到り、百より數へ放ち去つて、千に到りて、此身兀然として此の心寂然たる事、虛空と等し。斯の如くなる事久ふして、一息おのづから止まり出でず入らざる時、此の息八萬四千の毛竅の中より雲蒸し霧起るが如く、無始劫來の諸病自ら除き、諸障自然に除滅する事を明悟せん。譬へば盲人の忽然として眼を開くが如けん。此の時人に尋ねて路頭を指す事を用ひず、只要す、尋常言語を省略して、儞の元氣を長養せん事を。是の故に云ふ、目力を養ふ者は常に瞑し、耳根を養ふ者は常に飽き、心氣を養ふ者は常に黙とす。

(Hakuin 2000, pp. 135–39)

All the passages cited above from Japanese sources are direct translations of Chinese classics. Su Wen 素問 (Questions about origins) is a foundational chapter of the Huangdi Neijing 黃帝內經 (The Yellow Emperor’s Inner Classic). This passage describes an ideal state of life in which Zhēn Qi fills the entire body, resulting in complete health, vitality, and immunity. Some later Daoist practitioners believed this to be a manifestation of achieving the state of fetal breathing, wherein one becomes fully permeated with Yuán Qi. Fetal breathing techniques typically begin with adjusting mouth and nose breathing. According to textual records, practitioners will experience their breathing becoming progressively slower. Those who practice correctly may enter a state where mouth and nose respiration ceases, experiencing extreme emptiness, tranquility, and stillness in both body and mind—as if returning to the mother’s womb. Throughout history, many Daoist practitioners have used this approach in seeking enlightenment. Su Neihan 蘇内翰 (Su Shi 蘇軾, better known as Su Dongpo 蘇東坡, the renowned Song dynasty literatus; “nèihàn” being an honorific derived from his official title “Hànlín Xuéshì” 翰林學士), cited by Hakuin, is one example; the passage is recorded in works such as Dongpo Zhilin 東坡志林 and Su Shen Neihan Liangfang 蘇沈內翰良方. Peng Zu 彭祖, an immortal in Daoist culture, and the related quotation similarly embody the ideal effects of fetal breathing cultivation. The saying is sourced from classical Daoist texts on life-nurturing preserved in the Ming dynasty Zhengtong Daozang 正統道藏, such as Taiqing Daolin Shesheng Lun 太清道林攝生論.

From Hakuin’s expression in Yasen Kanna, we can see that he connected the practice of “Guarding the One” with the practice of “Fetal Breathing”. How should we understand this? It is noteworthy that although the method of Guarding the One and the Fetal Breathing emphasize different aspects in their textual expression, in the actual practice of Daoist cultivators, they are often complementary or practiced sequentially. For instance, the “method of contemplating a bean-sized object at the navel wheel” from the Mohe Zhiguan mentioned above requires making the breath regulated and even. The same volume also points out that if one settles the mind at the dāntián, then the breath become harmonized, highlighting the supportive relationship between mental concentration and breath regulation.

From the perspective of Daoist cultivation, both Fetal Breathing and Guarding the One are grounded in the profound ancient Chinese recognition of the relationship between “Spirit” (shén 神) and “Qi” (氣,is sometimes also used as “炁” in Daoist texts, where it usually refers to the original, primordial qi). The concepts of Spirit and Qi represent Daoist unique reflections on the mind–body relationship. Rooted in the previously mentioned cosmology of the Dao generating the myriad things, Daoism holds that “Spirit”, which governs consciousness, and “Qi”, which carries life energy, share the same origin. Although they have distinct names and characteristics in the postnatal (Conditioned) state, they actually influence each other. Daoist scriptures state: “When the Spirit moves, the Qi moves; only when the Spirit is within can the Qi be within.” 神行即炁行，神住即炁住。 “Spirit and Qi were originally one substance in the mother’s womb. After birth, they are pulled by external circumstances and desires, not even momentarily returning to their origin. One who knows this constantly extinguishes emotional thoughts, preventing the Spirit and Qi from coming and going, exiting and entering. If one can remain unforgetful and practice this over time, the Spirit will naturally abide.” 神之與炁，在母腹中本是一體之物，及生下為外境愛欲所牽，未嘗一息暫歸於本。人知此道，常泯絕情念，勿使神之出入去來，能不忘，久而習之，神自住矣。 (Huanzhen 1988, p. 869).

The above discussion arises from the fact that, in actual practice, Daoist practitioners discovered that calming the mind cannot rely on the mind alone, as subduing thoughts still constitutes a mental effort. Therefore, practitioners often use the rhythm of breathing as an expedient method; once they focus intently on the breath, they feel it becoming progressively steadier, and the mind naturally grows quiescent. Among the various schools of Daoism, the most systematic and detailed description of the combination and application of the practices of Guarding the One and Fetal Breathing is found in Internal Alchemy. Internal Alchemy practitioners typically use it as a fundamental training method. The following passage from Huang Yuanji’s 黃元吉 Leyutang Yulu 樂育堂語錄, a work by the Qing Dynasty Internal Alchemy scholar, serves as an example:

Recently, during practice, although the breath can be regulated, it ultimately has not yet returned to the state of utmost emptiness and great tranquility. Consequently, the Gate of the Xuán-Pìn 玄牝 still cannot manifest. Only by, day and night, regardless of having affairs or being without affairs, in change or in constancy, constantly directing the light of the Spirit (shénguāng 神光) straight down to the lower dāntián, and gathering both Spirit and Qi into the Mysterious-Mysterious Cavity (xuánxuán yīqiào 玄玄一竅). At first, you will feel each breath is heavy and labored; after a while, the breath will become soft and subtle, and you will enter a slightly calm state. After a long time, the breath will seem to exist yet not exist, and you will enter an even calmer state. When the breath has completely returned to the Spirit, and you can no longer feel its existence, only then can you reach a state of “great stability and stillness”, and only then can you obtain the “true medicinal herb” for Inner Alchemy. 近日用工，雖氣息能調，究未歸於虛極靜篤，則玄牝之門猶不能現象。惟於日夜之際，不論有事無事，處變處常，時時以神光直注下田，將神氣二者收斂於玄玄一竅之中。始則一呼一吸，猶覺粗壯；久則覺其微細，則少靜矣；又久則覺其若有若無，則更定矣。迨至氣息純返於神，全無氣息之可窺，斯時方為大定大靜，煉丹則有藥可采。

(Ge 2013, p. 104)

This passage clearly reveals the concrete application of Guarding the One and Fetal breathing as foundational practices in Internal Alchemy cultivation. Internal Alchemy practitioners stabilize their heart-mind and replenish their Yuán Qi through methods of regulating the breath and concentrating the spirit, thereby restoring physical health and laying the groundwork for entering a state of “utmost emptiness and steadfast tranquility” (xūjí jìngdǔ 虛極靜篤). The phrase originates from Chapter 16 of the Laozi: “Reach the utmost emptiness, hold fast to profound tranquility; as all things rise and fall, I observe their return to the origin.” 致虛極，守靜篤，萬物並作，吾以觀复。 (Laozi 2014, p. 61). This signifies that only within a state of profound stillness and stability can one commune with the Dao and thus apprehend the essence of all things. Internal Alchemy inherited this concept and developed a corresponding cultivation system in practice. The practitioner must reach this “great stability and stillness” (dàdìng dàjìng 大定大靜) to summon the fundamental and sole resource for achieving the immortal Golden Elixir: the Primordial Unity of Qi (xiāntiān yīqì 先天一炁). The specific connotations of this will be detailed in the next subsection. From the perspective of textual expression, emphasizing the “unification of Spirit and Qi” (shénqì héyī 神氣合一) and constructing a corresponding cultivation system is a distinctive feature of Daoist cultivation literature that sets it apart from general Zen sayings. Hakuin evidently integrated aspects of this. His repeatedly advocated method of “directing the heart-qi down to the Sea of Qi and the dāntián” corresponds, within the context of Daoist Internal Alchemy practice, precisely to the preliminary work described as “when the Spirit returns to the body, the Qi naturally returns”. 神返身中氣自回。 (Z. Chen 1988 p. 16). It aims to guide the outwardly scattered Spirit and Qi back to their source, restoring physical and mental health. Therefore, the method promoted by Hakuin serves, for those suffering from Zen sickness, as an expedient means to regulate the Heart and Kidneys and counteract this condition; viewed from the perspective of internal alchemy cultivation, it is the initial practice of attaining the Dao and becoming an immortal. This also explains why Hakuin, in texts such as Yasen Kanna, referred to his method as the “Secret Method of the Immortals’ Internal Alchemy”.

Of course, as evident from the above analysis, practices like Guarding the One and Fetal Breathing essentially belong to the preparatory stages of internal alchemy cultivation and are not exclusive to it. This naturally raises a question: Did Hakuin merely borrow such Daoist methods fragmentarily from various secondary sources and label them as the “internal alchemy”, or did he possess a relatively systematic understanding of Daoist internal alchemy doctrine, enabling him to grasp the physical and mental states of its different cultivation stages and thus apply them selectively and flexibly in his teaching? This article believes the latter to be the case. The following section will further analyze, from a textual perspective, its intellectual connection with the Southern School of Daoism to illustrate this point.

2.3. The Appropriation of Thought from the Southern School of Daoism

An examination of texts such as Yasen Kanna reveals that Zen Master Hakuin had likely studied the doctrines of the Southern School of Daoism. In his discussions on Daoist cultivation lineages and their core essentials, he frequently referenced content related to this Southern School. As a major school of internal alchemy during the Song and Yuan dynasties, the Southern School of Daoism was founded by Zhang Boduan 張伯端 in the Northern Song period. Through four generations of transmission—Shi Tai 石泰, Xue Daoguang 薛道光, Chen Nan 陳楠, and Bai Yuchan 白玉蟾—it formed a complete internal alchemy system (Gai 2020). Hakuin’s work exhibits an encounter with and selective appropriation of this tradition, an engagement that will be analyzed in the following subsections from the perspectives of core theory, lineage attribution, and practical method.

2.3.1. Adopting Bai Yuchan’s Summary of Internal Alchemy Practice

Hakuin repeatedly adapted and incorporated the teachings of the Southern School patriarchs into his own theoretical framework. Firstly, in the preface to Yasen Kanna, Hakuin summarizes the core idea of the entire text in a passage written in Japanese kana:

What is explained in this draft? It is said: Generally, the essential point of nurturing life and preserving longevity lies in refining their physical form. The essential point of refining the physical form lies in concentrating the Spirit and Qi to congeal within the dāntián and the Sea of Qi spaces. When the Spirit is concentrated, Qi gathers; when Qi gathers, the Elixir is formed; when the Elixir is formed, the physical form becomes stable; when the physical form is stable, the Spirit becomes complete. When the Spirit is complete, longevity is secured. This accords with the secret of the Immortals’ “Nine-cycle Reverted Elixir”. One must know that the elixir is ultimately not an external substance. It lies solely in lowering the Heart-Fire and filling the Sea of Qi and the dāntián. 稿中何の説く處ぞ。曰く、大凡生を養ひ長壽を保つの要、形を鍊るにしかず。形を鍊るの要、神氣をして丹田氣海の間に凝らさしむるにあり。神凝る則は氣聚る。氣聚る則は、即ち真丹成る。丹成る則は形固し。形固き則は神全し。神全き則は壽がし。是仙人九轉還丹の秘訣に契へり。須らく知るべし、丹は果して外物に非ざる事を。千萬唯心火を降下し、氣海丹田の間に充たしむるに有るらくのみ。

(Hakuin 2000, pp. 93–94)

This passage is Hakuin’s summary of the core idea of the entire work. In form, it is kana text of Chinese style, clearly translated from a Chinese original. Its Chinese source text can be found in Kanzanshi Sendai Kibun and Orategama. In Kanzanshi Sendai Kibun, Hakuin explicitly notes that this passage originates from “Bai Yuchan”. In fact, the middle part of this quotation is a direct quote from Bai Yuchan’s Xuanguan Xianmi Lun 玄關顯秘論 (Discourse on the Manifestation of the Mysterious Pass), while the rest is Hakuin’s interpretation. Bai Yuchan’s original text (including the following sentences) is as follows:

For those who now practice this principle, it is better to first refine their physical form. The essence of refining the physical form lies in concentrating the Spirit; when the Spirit is concentrated, Qi gathers; when Qi gathers, the Elixir is formed; when the Elixir is formed, the physical form becomes stable; when the physical form is stable, the Spirit becomes complete. Therefore, True Person Tan said: “Forget the physical form to nurture Qi; forget the Qi to nurture the Spirit; forget the Spirit to nurture emptiness.” 今修此理者，不若先煉形。煉形之妙，在乎凝神，神凝則氣聚，氣聚則丹成，丹成則形固，形固則神全。故譚真人云：“忘形以養氣，忘氣以養神，忘神以養虛。”

(Bai 1989, p. 1)

A comparison of the two texts shows that Bai Yuchan’s passage provided the theoretical basis for Hakuin’s practice of “lowering the heart-fire”. However, Hakuin’s citation and interpretation do not fully align with Bai Yuchan’s original intent. Bai Yuchan’s statement aims to clarify the complete sequence of internal alchemy cultivation, whose ultimate purpose is to transcend all attachment to form and dualistic discrimination, returning to the source of the Dao itself. In contrast, Hakuin’s emphasis falls on the preliminary practice of “concentrating the Spirit and gathering the Qi”. Notably, after the line “when the physical form is stable, the Spirit becomes complete”, Hakuin adds the phrase “when the Spirit is complete, longevity is secured”, indicating his intent to guide readers toward strengthening the body, preserving health, and extending life through cultivation. Furthermore, Hakuin did not quote the techniques and secrets related to “forgetting” in the second half of Bai Yuchan’s original text.

2.3.2. Attributing the Method to Shi Tai

The statement “when the Spirit is concentrated, Qi gathers…” frequently appears in Hakuin’s writings and has also been disseminated through art forms such as calligraphy. A calligraphy work at the Waseda University Aizu Yaichi Museum embodies this. Interestingly, when Hakuin created this work, he did not attribute it to Bai Yuchan or Hakuyūshi, but instead titled it “Words Master Shi Tai Spoken to Wu Qichu”. This detail can be seen as further evidence of the interaction between Hakuin’s thought and the Southern School of Daoism. Records of “Wu Qichu” 吳契初 and “Shi Tai” 石臺 also appear in Yasen Kanna, as follows:

Long ago, Wu Qichu visited Master Shi Tai. After fasting, he inquired about the secrets of alchemy. The master said: “I possess the secret of the Primordial Mysterious True Elixir. It cannot be transmitted to anyone without the highest aptitude. It was passed down from Huang Chengzi to the Yellow Emperor, who received it after three times seven-day fasts. Beyond the Great Dao, there is no True Elixir; beyond the True Elixir, there is no Great Dao. There exists a method called the Five Leakage-Free Dharmas. When you rid yourself of the Six Sensual Desires and your five sense organs each forget their respective functions, the undifferentiated, primordial genuine Qi will seem to fill your entire field of vision. This is what the Great White Daoist meant by ‘merging one’s own heaven with the heaven one serves’ 以我之天合所事之天; it is what Mencius called ‘the vast and righteous Qi’. (hàorán zhī qì 浩然之氣) Guide this Qi and store it between the sacral chakra and the dāntián. Over the years, guard this, abide in this Oneness, and nourish it so that it has no place to go. One day, when the alchemical furnace is suddenly overturned, the inside, the outside, the middle, the eight directions, and the four dimensions will all become one single Great Reverted Elixir (dà huándān 大還丹). At this moment, you will realize for the first time that you were born before heaven and earth, yet it seems as if you were never born, and will not die after the void—you will become a true immortal.” 昔し吳契初石臺先生に見ゆ。齋戒して鍊丹の術を問ふ。先生の云く、我に元氣真丹の神秘あり。上々の器にあらさるよりんは得て傳ふべからず。古しへ黃成子是を以て黃帝に傳ふ。帝三七齋戒して是を受く、夫大道の外に真丹なく、真丹の外に大道なし。蓋し五無漏の法あり。儞の六欲を去け、五官各各其職を忘るる則は、混然たる本源の真氣彷彿として、目前に充つ、是れ彼の大白道人の謂ゆる我が天を以て事ふる所の天に合する者なり。孟軻氏の謂ゆる浩然の氣、是れをひきいて臍輪氣海丹田の間に藏めて、歳月を重ねて、是れを守つて、守一にし去り、是れを養ふて無適にし去つて、一朝乍ち丹竈を掀翻する則は、内外中間八紘四維、總に是れ一枚の大還丹。此の時に當つて、初めて自己即ち是れ天地に先ちて生せず、虛空に後れて死せざる底の真個長生久視の大神仙なる事を覺得せん。

(Hakuin 2000, pp. 121–23)

Hakuin used this passage to introduce the lineage, content, and purpose of Internal Alchemy doctrine. The “Huang Chengzi” 黃成子 in the quotation is a misreading of “Guang Chengzi” 廣成子. The stories of the Yellow Emperor and Guang Chengzi is extremely common in Daoist literature and are considered an important source of Daoist transmission. However, regarding the two figures Wu Qichu and Shi Tai, no direct records seem to appear in Daoist texts such as the Zhengtong Daozang 正統道藏. Nonetheless, I discovered a relevant entry in the first volume of Ren Tian Baojian 人天寶鑒 (The Precious Mirror of Humanity and Heaven), compiled by the monk Tan Xiu 曇秀:

The Daoist Wu Qichu was a native of Zhuyang in Guo. He served as the magistrate of Heqing. Having been impeached by an inspector, he withdrew to Mount Song. There he met Master Shi Tai. Wu asked: “May I hear about the Dao of Emptiness and Nothingness?” Shi said: “The ancient awakened ones had the Five Leakage-Free Dharmas. When the eyes do not look, the Hún 魂 remains in the liver. When the ears do not hear, the Jīng 精 remains in the kidneys. When the tongue does not speak, the Shén 神 remains in the heart. When the nose does not smell, the Pò 魄 remains in the lungs. When the four limbs do not move, the Yì 意 remains in the spleen. These five, interacting and blending, transform into One Qi, gathering at the Three Passes. This is called lead and mercury. Seek it within your own body; there is no need to seek it elsewhere.” Wu received and practiced the formula. After a long time, his practice succeeded. 道士吳契初，虢之朱陽人，為河清令，以部使者所劾，隱於嵩山，尋遇石泰先生。吳問曰：”虛無之道可得聞乎？”石曰：”先覺有五無漏法。眼不視，魂在肝；耳不聞，精在腎；舌不聲，神在心；鼻不香，魄在肺；四肢不動，意在脾。五者相與混融，化為一炁，聚於三關，名曰鉛汞。但身中求之，不必求於他也。”吳稟受訣，久之功成。

(Tan 1670, p. 26)

From this, we know that Wu Qichu was actually an internal alchemy practitioner who inherited the methods of the Southern School. He remained obscure for a long time because he was not recorded in mainstream Daoist texts. This record clearly shows his lineage from Shi Tai 石泰 (1021–1158). Shi Tai was a Song dynasty Daoist, later revered as the Second Patriarch of the Southern School and a direct disciple of the Southern School founder, Zhang Boduan (984–1082). Comparing this record with Hakuin’s writings, it can be determined that the “tái” 臺 is actually a homophonic scribal error for “tài” 泰. This error has long prevented academic circles from appreciating his connection with the Southern School of Daoism.

2.3.3. Adapting the “Five Leakage-Free Dharmas” Practice

Having clarified the identities, we can analyze the connection between the two quotations through their specific cultivation methods. Both Yasen Kanna and The Precious Mirror of Humanity and Heaven mention the “Five Leakage-Free Dharmas”. 五無漏法 Although the term “leakage-free” 无漏 is commonly used in Buddhism, in this context, it carries a stronger Daoist internal cultivation connotation. This method actually originates from the Southern School’s First Patriarch, Zhang Boduan. The preface to Jindan Sibaizi 金丹四百字 (Four Hundred Words on the Golden Elixir), included in the Ming dynasty Zhengtong Daozang, contains an almost identical discussion:

It is called ‘leakage-free’ because the Hún 魂 remains in the liver and does not leak through the eyes; the Pò 魄 remains in the lungs and does not leak through the nose; the Shén 神 remains in the heart and does not leak through the mouth; the Jīng 精 remains in the kidneys and does not leak through the ears; the Yì 意 remains in the spleen and does not leak through the orifices of the four limbs. Therefore, it is called leakage-free. Jing, Shen, Hun, Po, and Yi interact, blend, and transform into One Qi. It cannot be seen or heard, nor does it have any name or form. Therefore, it is called Emptiness and Nothingness. 以魂在肝而不從眼漏，魄在肺而不從鼻漏，神在心而不從口漏，精在腎而不從耳漏，意在脾而不從四肢孔竅漏，故曰無漏。精、神、魂、魄、意相與混融，化為一氣，不可見聞，亦無名狀，故曰虛無。

(B. Zhang 1988, p. 161)

The core of this method lies in stopping the functions of the senses, reversing the tendency of postnatal Yuán Qi to dissipate, and returning to a state of emptiness and stillness to merge with the Dao. Notably, the description of the experiential effect of this practice is transforms into One Qi. This One Qi precisely the “One” in Laozi’s saying “the Dao generates the One” 道生一 and it is also what Huang Yuanji referred to as the “true medicinal herb” of internal alchemy cultivation—the Primordial Unity of Qi (xiāntiān yīqì先天一炁). Also called “Ancestral Qi” (zǔqì祖炁) or “Primordial Yang” (yuányáng元陽), it is the cosmic substance and source of life that transcends postnatal Yin–Yang and the Five Phases. It is the fundamental resource for achieving transcendence through internal alchemy cultivation.

It is necessary to clarify that this “Primordial Unity of Qi” is not the same concept as the “Yuán Qi” discussed earlier. The previous sections introduced the forward cosmogony of “the Dao generates the One, the One generates the Two…” 道生一，一生二 Internal alchemy seeks this path, emphasizing reverse cultivation, returning to the origin, thus strictly distinguishing between the Primordial (xiāntiān 先天) and the Conditioned (hòutiān 後天). The “turbid substances” within the conditioned realm—including the breath-qi within the human body, the procreative essence, blood, and even the Yuán Qi as the motive force of life—cannot serve as the transcendent basis for alchemical refinement and immortal attainment. This is because all these belong to the realm after “the Dao generates the One”. “The One generates the Two” marks the opening of the dualistic opposition of Yin and Yang, signifying finitude and termination. Any existence within this dimension, no matter how much is accumulated, cannot achieve infinite and absolute life. Only by using the “One” that exists prior to the differentiation of Yin and Yang can one attain the state described by Hakuin as “born before Heaven and Earth and immortal after the Void”. Therefore, the Southern School of Daoism emphasizes that one must adopt the “Primordial Unity of Qi” as the elixir and return to the formless source.

Following the teaching of the Laozi to “reach the utmost emptiness, hold fast to profound tranquility”, internal alchemists believe that the “Primordial Unity of Qi” can only manifest within the empty and tranquil state where all postnatal life activities and dualistic thinking have ceased. This “Primordial Unity of Qi” cannot be encompassed by the concept of material energy; it points more towards a state of being. Expressions like “connecting with Primordial Unity of Qi” are metaphors, not referring to the manifestation of some energy within or outside the body. Therefore, Daoist theorists can only forcibly name it as “the Primordial Unity of Qi comes from within Emptiness and Nothingness”. 先天一炁從虛無中來 This also explains why Hakuin says the primordial genuine Qi only “seem to” appears. For if it were truly and concretely before the eyes, it would have already fallen into dualistic opposition, indicating the practitioner has not yet entered the state of the “One”. The true “Primordial Unity of Qi” naturally reveals itself only when the practitioner reaches the empty and tranquil state of “no thought, no reflection”, “body and mind utterly still”, unaware of the self, and in a state of undifferentiated chaos. Returning to the earlier quotation from Bai Yuchan’s Xuanguan Xianmi Lun, the phrase “those who now practice this principle” refer to those who understand and connect with “Primordial Unity of Qi”. This also clarifies why Bai Yuchan, while presenting the active practices of “refining the physical form”, simultaneously emphasizes the essential formulas of “forgetting the form”, “forgetting the Qi”, and “forgetting the Spirit”.

Within the Daoist cultivation system, after communing with the Primordial Unity of Qi, one formally enters the core stage of internal alchemy cultivation. This involves the accumulation and nurturing of this “medicinal herb”, as well as the application of “fire times and degrees” until the Great Golden Elixir is fully accomplished. These processes are extremely subtle. Most internal alchemists emphasize oral transmission from mind to mind, which cannot be fully conveyed in writing. From the records in Yasen Kanna, it appears that Zen Master Hakuin did not elaborate on this.

Reaching this point in the analysis allows for a clear understanding of the basic content of Zen Master Hakuin’s “incorporating Daoist Practices into Zen”. What he absorbed and promoted primarily stemmed from the preparatory-stage practices within the Daoist internal alchemy system. Their purpose was to help Zen practitioners restore physical and mental health, establish a stable foundation for cultivation, and further enter a state of highly focused mental concentration. This point is also corroborated in Orategama. Hakuin stated:

Generally, when it comes to the actual substance, the sages of the Three Teachings are largely in agreement. Although there are differences in the height of attainment depending on the depth and refinement of their progression, the initial step of their orientation is equal. The Confucians call this place the “Ultimate Good”. Daoism calls it “Guarding the One without deviation”. In Shintō, it is transmitted as the Plain of High Heaven (Takama-ga-hara). In Tiantai, it is the great matter of the One Thought for Ten Thousand Years cessation-and-contemplation. In Shingon, it is the contemplation of the letter ‘Ā’ as unproduced. The patriarchs of each school encourage reaching the state of sitting meditation, chanting sutras, or reciting invocations—all are expedient means guiding one to the state of the undisturbed mind and purity without mixture. 大凡ソ三教ノ聖人ニ實處ニ至リテハ大段同ジ。其ノ進趣ノ淺深精粗ニ依リテ得カ高下ハ有ルベケレドモ、最初ノ一步ハ趣キ等シ。儒門ニハ此ノ處ヲ至善ト云ヒ、未發ノ中ト云。道教ニハ守一無適ト云イ。神家者ハ高間ガ原ト相傳ス。天台ニハ一念萬年止觀ノ大事トス。真言ニハ阿字不生ノ觀法ト云イ。家々ノ祖師達ノ坐禪ヲ勸、誦經ヲ勸メ玉フモ、誦ミ〻唱ヘ〻テ、一心不亂、純一無雜ノ田地ニ至ラシメン方便ナラズヤ。

(Hakuin 2001, pp. 359–60)

Nevertheless, Zen Master Hakuin also had a unique understanding of the subsequent stages of internal alchemy cultivation. This can be seen from his innovative adaptations when teaching and practicing these Daoist methods. As a Zen master, Hakuin did not simply copy Daoist techniques. Based on his Zen standpoint and the practical needs of his audience, he interpreted, selected, and transformed these methods with his personal characteristics, ensuring the practice did not deviate from the correct path of Buddhist Zen cultivation. The following section will analyze this.

2.4. Transformation Within the Zen Context

Although Hakuin cites Daoist classics in Yasen kanna, introducing practices like Guarding the One and Fetal Breathing, at the level of concrete practice, he demonstrates unique insight as an enlightened Zen master. In the book’s preface, he devised a particularly ingenious method for concentrating the mind, as follows:

My Sea of Qi, dāntián, waist, feet, and soles—all are my Original Face. What nostrils does this Face have? My Sea of Qi and dāntián—all are my Original Home. What news is there from this Home? My Sea of Qi and dāntián—all are my Mind-Only Pure Land. What adornments does this Pure Land have? My Sea of Qi and dāntián—all are the Amitabha of my own Mind. What Dharma does this Amitabha preach? One should constantly fantasize in this manner, turning it over and over. When the effects of this fantasizing accumulates, the Yuán Qi of one’s whole body will, before one knows it, become sufficient within the area of the waist, feet, and soles. The area below the navel will be solid, like a new inflated leather ball. 我が此の氣海丹田腰脚足心、總に是れ我が本來の面目、面目何の鼻孔かある。我が此の氣海丹田、總に是れ我が本分の家郷、家郷何の消息かある。我が此の氣海丹田、總に是れ我が唯心の淨土、淨土何の莊嚴かある。我が此の氣海丹田、總に是れ我が己心の彌陀、彌陀何の法をか説くと、打返し打返し常に斯の如く妄想すべし。妄想の功果積らば、一身の元氣いつしか腰脚足心の間に充足して、臍下瓠然たる事、未だ篠打せざる鞠の如けん。

(Hakuin 2000, pp. 85–87)

The following analysis attempts to understand this method from two perspectives. First, compared to the traditional method of “fastening the mind to one place” found in the Mohe Zhiguan, the “Sea of Qi, dāntián, waist, feet, and soles” proposed by Hakuin here is actually a comprehensive focus on multiple parts of the body. This design likely aims to guide beginners in avoiding the drawbacks of fixating on a single point. The path of mental concentration from the Sea of Qi and dāntián down to the soles also helps practitioners experience the sensation of consciousness and energy flowing from top to bottom. This point can be cross-referenced with the “Soft-Butter Method” 軟酥法 described in Yasen Kanna. After introducing traditional methods from texts like the Mohe Zhiguan, Hakuin specifically introduces this method: “If during meditation the practitioner’s Four Great Elements are disharmonious, and both body and mind feel fatigued, one should resolve to form this contemplation. Imagine soft butter, pure in color and fragrance, the size of a duck’s egg, suddenly placed on the crown of the head. Its scent is subtle and wondrous, moistening the entire head, seeping down slowly over the two shoulders and arms, the two breasts, the area between the chest and diaphragm, the lungs, liver, stomach, intestines, spine, and hip bones, successively saturating as it goes. At this time, the five accumulations and six gatherings in the chest, hernias, aggregates, and pains descend following the mind, like water flowing downward, with a distinct sound, circulating throughout the body, warmly moistening both feet, stopping at the soles. The practitioner should then cultivate this visualization again: the slowly seeping residual liquid accumulates, clear and warm, as if a skilled physician has collected various precious herbs and brewed them into a medicinal soup, and filling a bathtub, and I am immersing the area below the navel chakra in it. When forming this contemplation, since it is solely manifested by the mind, the nose faculty suddenly smells a rare fragrance, the body faculty immediately experiences a wonderfully soft and pleasant touch, and body and mind become regulated and comfortable, far surpassing the state of one’s twenties or thirties. At this time, accumulations dissolve and disperse, the stomach and intestines are harmonized, and one unconsciously notices the skin gaining luster. If one diligently practices without laziness, what illness will not be cured, what virtue not accumulated, what immortal state not realized, what Dao not accomplished?” (Hakuin 2000, pp. 141–43).

This method also shows a tendency to guide consciousness in a downward flow through the body. Hakuin stated in Yasen Kanna that “the Āgamas contain the method of using Butter Method”, but my own search or consultation of research by scholars like Mr. Yoshizawa has not found a similar method in Āgama scriptures. A similar “Butter Pouring Method” 灌酥法 exists in the Methods for Curing Zen Sickness 治禪病法 in the Taisho Tripiṭaka 大正藏, but it also differs significantly from Hakuin’s description. However, methods for guiding energy flow between the dāntián and the soles of the feet are frequently found in Daoist classics, such as the “Western Queen Mother’s Firm Holding Method transmitted by Taishang”.太上傳西王母握固法 The following is a short excerpt: “Sit with the body upright. Visualize a red sun in the heart, the size of a coin. As it becomes slightly warm, let it directly descend from the left flank down to the dāntián, then to the sole of the left foot. When the sole feels slightly warm, again visualize the fire burning up from below to the dāntián below the navel, gradually moving to the right foot. Then, when the sole feels slightly warm, and visualize the flames burning from the navel to your dāntián…” 正身端坐，想心中紅日，輸如錢大。稍暖，從左脅直放下丹田，下左足心。稍暖，又存火從下燒上臍下丹田，漸漸方過右足。又候腳心稍暖，從下發火燒至丹田…… (Xiuzhen Shishu 1988, p. 707). Hakuin did not elaborate further on the deeper meaning or origin of the Soft Butter Method. This article speculates that it may have been a method created by Hakuin or his teacher based on personal insights combined with classical terminology, intended to assist the aforementioned methods of concentration and breath control. This will be discussed in detail later in this article.

Second, when he instructed practitioners to concentrate their mind on the dāntián and other such locations, he did not intend for these to be cultivated as actual, substantial cavities. Rather, he established them as anchor points for a kōan 公案. Just as he designed the critical phrase: “My Sea of Qi and dāntián—all are my Original Home. What news is there from this Home?” This immediately guided the practitioner, in the very moment of concentrating the spirit, to investigate the inherent, intense tension of the paradox: “How can this specific location within the physical form be a distant, intangible Original Home?” This acute contradictory tension is precisely where the dynamic pivot of Hakuin’s Zen method lies.

He skillfully utilized the state of cessation of random thoughts induced by “concentrating the spirit” as the samādhi power necessary for investigating a critical phrase. Simultaneously, he implanted the doubt of the critical phrase directly into this very samādhi, ensuring it pointed from the outset toward the dismantling of “view or belief that there is a real self” (shēnjiàn 身見) and “attachment to dharmas” (fǎzhí 法執). What’s even more remarkable is Hakuin’s keen understanding of the unique physical and mental state experienced when connecting with the Primordial Unity of Qi in the context of Daoist internal alchemy practice. In this state, practitioners transcend dualistic opposition and directly intuit the source of creation, a condition that indeed shares common ground with the Zen state of “illuminating the mind and seeing one’s true nature” (míngxīn jiànxìng 明心見性). He adeptly transformed this juncture into a point of entry for Zen awakening, guiding practitioners to investigate the critical phrase amidst the ultimate experience of psychosomatic transformation, thereby abruptly severing ignorance. According to personal accounts in texts like Yasen Kanna, he himself benefited from this, attaining numerous great and small awakenings.

Thus, the profound subtlety of this method lies in how it presupposes and guides towards the ultimate transcendence from the very start, infusing the entire cultivation process with the wisdom of the final goal. Its benefits are thus both universal and profound: For ordinary people seeking merely to regulate body and mind, even without realizing the Primordial Unity of Qi, the practices of mental concentration and breath regulation alone can yield restorative effects. For those with sharp faculties and understanding of the principles, it allows them to maintain physical and mental health while progressively transforming the experiences of Daoist cultivation into opportunities for advancing through the Zen barrier, steadily progressing on the path to enlightenment. Of course, the deeper meaning and specific pedagogical implementations require further elucidation through combining Hakuin’s broader recorded sayings and teaching practices.

3. The Later Influence of Hakuin’s Incorporation of Daoism into Zen and the Response from Chinese Cultivation Community

Hakuin’s practice of incorporating Daoist methods into Zen not only provided an effective remedy for the Zen sickness prevalent among Zen monks of his time but also opened a practical path for the physical and mental cultivation of ordinary people. It popularized and made accessible originally profound cultivation methods, thereby exerting a far-reaching influence in Japan from the Edo period onward. This system of cultivation, integrating Eastern wisdom, did not stop within Zen monasteries. During the modernization process, it was adopted, transformed, and reinterpreted by a group of cultivation theorists with scientific perspectives, further evolving into physical and mental health methods suited to modern needs. This formed a cultural transmission and evolution lineage spanning religions, regions, and eras.

3.1. The Establishment of the Three Great Health Methods in the Meiji Period

During the Meiji period in Japan, with the accumulation of modern technology and material wealth, the physical and mental health of the general public became increasingly prominent. Against this backdrop, a group of insightful individuals attempted to draw upon resources from traditional Eastern self-cultivation techniques, combining personal experience with scientific concepts to construct a set of methods for harmonizing body and mind to meet the needs of modern people. Among them, the “Abdominal Breathing Method” (Fukushiki Kokyūhō 腹式呼吸法) proposed by Futaki Kenzo 二木謙三 (1873–1966), the “Harmonizing Method” (Chōwahō 調和法) advocated by Fujita Reisai 藤田霊齋 (1868–1957), and the “Okada-style Quiet Sitting Method” (Okada-shiki seiza-hō 岡田式靜坐法) promoted by Okada Torajirō 岡田虎二郎 (1872–1920), active during the same period, were collectively known as the “Three Great Meiji Health Methods” (Matsuo 1914; Nishikawa 1916). All three of these figures suffered from frail health and frequent illness in their early years, but later recovered through practicing quiet sitting, subsequently developing unique psychosomatic philosophies and personal charisma. Both Futaki Kenzo and Fujita Reisai explicitly stated in their writings that their methods of quiet sitting were drawn from the inspiration of Hakuin. Although Okada Torajirō did not author any works personally, the influence of Hakuin is discernible from his disciples’ accounts and his training methodology. Although all three emphasized regulating breathing and focusing on the abdomen during quiet sitting, they differed significantly in their specific techniques.

Futaki Kenzo, as a medical doctor, actively promoted the Abdominal Breathing Method through lectures and papers while engaged in scientific research. For instance, in his report, he introduced: “A unique way of nurturing life has been transmitted in the East since ancient times. It is said to cure incurable diseases, enable people to be reborn, prolong life, and stay free from illness. It is called the ‘Contemplation of Counting Breaths’ 數息観, the ‘Vipassanā Method’ 內觀法, the ‘Method of Gathering Qi at the Sea of Qi and Dāntián’ 氣海丹田收氣法, the ‘Method of Refining the Elixir for Agelessness and Immortality’ 錬丹不老不死法, etc. In Japan, this method was revived by the Zen master Hakuin. Hakuin received it from his teacher Hakuyūshi, and it has been transmitted through successive generations of Zen families.” Regarding the specific content of this cultivation method, Futaki Kenzo believed: “To put it in one word, it is a method of making the breath of respiration finer and longer, drawing it down to the lower abdomen, bulging the area below the navel, and infusing it with strength.” (Futaki 1933, p. 87) From this statement, one can roughly see his understanding of the health-preservation techniques introduced in Hakuin’s Yasen kanna. Based on this, he named this cultivation method the “Abdominal Breathing Method” and established the following key points for beginner training:

Posture: Primarily seated postures such as kneeling sitting 跪坐 or cross-legged sitting 盤坐, though sitting on a chair is also acceptable. Spine straight, shoulders pulled back, chest open, abdomen protruding forward; fix the muscles and joints of the waist and abdomen; relax the shoulder blades and chest; keep the head upright. Place hands on thighs, palms up, crossed and stacked; close eyes and mouth; concentrate the spirit and quiet thoughts.

Breathing Method: Breathing should be calm, slow, and deep. Start with exhalation, contracting the chest and abdomen to expel air as much as possible. Pause briefly after exhalation, then inhale slowly. During inhalation, the chest and abdomen expand synchronously, with particular emphasis on the lower abdomen bulging out. Pause briefly after inhalation is complete, then switch to exhalation.

Speed and Rhythm: One breath cycle includes exhalation, inhalation, and rest periods, totaling about four to six times per minute. Frequency can be adjusted based on proficiency and constitution. Maintain natural chest-abdominal breathing outside of practice.

Duration: Each practice session should last about fifteen to thirty minutes, two to three times daily. After finishing, it is advisable to rest by walking slowly.

Abdominal Pressure Training 腹壓訓練: During inhalation, the abdominal wall slightly resists bulging; during exhalation, the diaphragm slightly resists rising. Gradually increase abdominal pressure, making the lower abdomen firm and less prone to sinking.

(Futaki 1933, p. 97)

Regarding the breathing method, Futaki advocated “direct breathing” 順式呼吸, where the abdomen expands during inhalation and contracts during exhalation. He emphasized the full expansion of the lungs during deep breathing and pointed out the key role of the diaphragm in this process. During breathing, Futaki stressed the importance of applying force, for example stating: “Whether inhaling or exhaling, it is crucial to inject strength and maintain a uniform, sustained rhythm.” He also said: “When practicing this breathing method, one must first focus on infusing abdominal strength. However, one must not deliberately hold the breath. Maintain the abdomen full of strength while allowing the breath to flow naturally—without preset counts, unbound by form, solely following nature to reach a state of stillness and stability. Initially, one can control the depth of breath at will, gradually reaching a state unmoved by activity or stillness, eventually reaching a point where one is unaware of the moments of the breath’s exit and entry. At that time, one can reach an extremely mysterious and wonderful state.” (Futaki 1936, p. 50) Futaki Kenzo also invented an “abdominal pressure meter”, discovered the importance of abdominal pressure for human health through comparative experiments, and developed training methods such as the “Abdominal Pressure Fixation Method”. For abdominal breathing training, Futaki claimed that “only eighty percent effort is needed”, with specifics depending on proficiency and individual disposition. (Futaki 1936, p. 44) He rationally pointed out that this method alone could not cure all diseases, thus advocating its combination with the cultivation of health habits like a brown rice vegetarian diet and regular routine.

As a medical doctor and an important representative of modern Japanese medicine at the time, Kenzo Futaki’s theories had a distinct scientific inclination. As he stated: “In the East, although abdominal breathing was advocated thousands of years ago, the explanations were limited to Yin-Yang theory; I have not heard of explanations on physiological or pathological levels.” (Futaki 1936, p. 99) To this end, he conducted much research, for instance, systematically explaining the health benefits of abdominal breathing from the perspectives of blood circulation and abdominal nerves. Kenzo Futaki’s background as a medical doctor gave his theories considerable persuasiveness and also provided, to some extent, scientific justification for the cultivation methods of Fujita and Okada.

Fujita Reisai founded the “Way of Harmony” (Chōwadō 調和道) and authored works while accepting disciples, who numbered in the tens of thousands and spanned various social strata, including influential figures. This was facilitated by his association with Ōkuma Shigenobu 大隈重信, the Prime Minister of Japan, who presented Fujita’s writings on cultivation to the Tennō, garnering imperial praise. Fujita authored several classics on self-cultivation, including Theory of Mind-Body Cultivation (Shinshin Shūyōron 身心修養論) and Method of Harmonizing Breath and Mind (Sokushin Chōwahō 息心調和法). He explained his method in his writings: “‘The Harmonizing Method’ is the abbreviated name; the full name is the ‘Method of Harmonizing Breath, Abdomen, and Mind’ or the ‘Method of Harmonizing Breath and Mind’.” The nomenclature itself reveals the focus of his cultivation theory: the harmonization of breath, abdomen, and mind. On this, he elaborated: “Breath is the foundation of life, the abdomen is the dwelling of life, the mind is the master of life… Therefore, the operations of breath, abdomen, and mind must conform to natural law and achieve a harmonious state.” (Fujita 1927, p. 3-1)

Fujita’s instructional system was relatively systematic, divided into three levels: Initial Transmission 初傳, Middle Transmission 中傳, and Secret Transmission 奧傳. The Initial Transmission focused on mind–body harmonization, the Middle Transmission advanced to strengthening, and the Secret Transmission relied on oral instruction. In terms of specific content, it could be divided into three parts: regulating the body, regulating the breath, and regulating the mind.

Broadly speaking, his methods for regulating the body and breath aligned with Kenzo Futaki’s, being based on an upright sitting posture adaptable to personal habit and advocating direct breathing. During the cultivation process, he divided breath training into three levels: “Effortful Breathing”, “Dāntián Breathing”, and “Body Breathing”. The ultimate goal, “Body Breathing”, resembles the Daoist Fetal Breathing.

The distinctive feature of Fujita’s cultivation theory lay in regulating the mind, which he also termed mental power training, emphasizing the use of kōan. He pointed out: “Those who wish to practice this cultivation method must, at the beginning of their practice, first select a kōan. The kōan constitutes the fundamental essence of this cultivation method.” Fujita clarified that the “kōan” referred to here is not the profound and obscure terminology of Zen, but concise and powerful words or phrases such as “Strong” 強壯, “Full of courage” 渾身是膽, “Namo Amituofo” 南無阿彌陀佛, or “Kind” 善, from which practitioners could choose according to their preference. Subsequently, practitioners, during quiet sitting, would place this kōan with their intention at the dāntián below the abdomen, as if reading it in their abdomen. Fujita calls this the “abdominal reading method”. According to Fujita’s explanation, through frequent training, practitioners could eventually attain life states such as “the dāntián emitting light” 丹田光明 and “the kōan becoming active”公案活躍, regarded as signs of successful training (Fujita 1908, pp. 115–16).

Torajirō Okada was as renowned as Fujita Reisai, likewise famous for teaching quiet sitting and possessing a large following of disciples. In 1911, Jitsugyō no Nihon Sha 実業之日本社 began serializing the so-called “Okada-style Quiet Sitting Method”, attracting widespread attention. By the end of the Meiji era, dozens of books on the Okada-style method had been published, and numerous magazines and newspapers featured his techniques, leading many to emulate them. However, none of these writings were authored by Okada himself. His disciples stated that he absolutely refused to write, believing the method of quiet sitting could not be conveyed through writing. Consequently, the published works on the Okada-style method actually stem from the personal experiences and insights of his disciples. Among these, the more detailed accounts include Kishimoto Nobutake’s 岸本能武太 Three Years of Quiet Sitting (Seiza Sannen 靜坐三年) and Hashimoto Gosaku’s 橋本五作 The Power of the Okada-style Quiet Sitting Method (Okada-shiki seiza no chikara 岡田式静坐の力). Both received direct instruction from Okada, so their writings are considered relatively closer to the original form of the Okada-style method.

In terms of cultivation approach, the Okada-style Quiet Sitting Method fundamentally differed from the methods of Futaki and Fujita, emphasizing “Reverse Breathing” 逆式呼吸 and “concentrating strength in the abdomen” 腹力集中. For example, Kishimoto discusses this in Three Years of Quiet Sitting: “I wish to summarize the essence of the Quiet Sitting Method as the ‘Abdominal Strength Method’ 腹力法. By this, I mean gathering the strength of the entire body at the dāntián below the navel. I believe this ‘Abdominal Strength Method’ is precisely the beginning and the end of the Okada-style Quiet Sitting method. All issues related to the method—for instance, its three major characteristics: (1) the posture of quiet sitting; (2) reverse breathing; (3) the swaying of the body—both originate from and return to this point. When the strength of the whole body is concentrated at the dāntián below the navel, and the body’s center is stabilized there, then the person’s body will naturally become healthy, and their spirit will naturally become healthy. This is the fundamental proposition of the Okada-style Quiet Sitting Method; herein lies its essential principle.” (Kishimoto 1916, pp. 26–27).

This passage reflects Kishimoto’s understanding of the Okada-style method. He summarized three major characteristics: First, the posture for quiet sitting, specified in the book as the traditional Japanese kneeling-seated posture. Second, Reverse Breathing. Three Years of Quiet Sitting states: “In ordinary breathing, inhalation first causes the lungs to expand, followed by the abdomen gradually bulging; exhalation causes the abdomen to gradually concave, culminating in the contraction of the lungs themselves. When the abdomen contracts, the abdominal force relaxes accordingly—and this is the ordinary breathing method. The Okada-style breathing method takes the constant preservation of abdominal strength without leakage as its essential principle. Therefore, during inhalation, one naturally must not allow the abdomen to concave, and during exhalation, one must especially avoid abdominal contraction. Because ordinary breathing has ingrained the habit of contracting the abdomen during exhalation, to break this habit, one must completely reverse the breathing pattern: during exhalation, bulge the abdomen with more force than during inhalation. This breathing method is the opposite of conventional breathing; hence, it is called Reverse Breathing.” (Kishimoto 1916, pp. 96–98). This method is the opposite of the abdominal breathing methods advocated by Futaki and Fujita. Furthermore, Kishimoto emphasized that exhalation should be long and inhalation should be short, which also differed from Futaki and Fujita’s advocacy of both slow, elongated exhalation and inhalation. Third, bodily swaying. This refers to the feeling that the body seems to sense some kind of internal energy during training, causing it to sway automatically and unconsciously; Kishimoto believes this is one of the signs of effective practice and talent.

It is important to note that Three Years of Quiet Sitting represents only Kishimoto’s personal experiences and insights, which may not fully capture the essence of the Okada-style method. In the later published The Power of the Okada-style Quiet Sitting Method, the author Hashimoto recorded his conversation with Okada, subtly noting that while Kishimoto’s writings based on three years of practice were already quite detailed, the relatively short duration of his practice meant his works failed to fully embody the true essence of Okada-style Quiet Sitting Method; Okada agreed. The specific content of The Power of the Okada-style Quiet Sitting Method also reveals Hashimoto’s intent to supplement and correct some of the expressions in Three Years of Quiet Sitting. For instance, when discussing “Quiet Sitting and Swaying”, he points out that some practitioners deliberately pursue swaying with large amplitudes, which is incorrect. Additionally, the book emphasizes the importance of direct instruction, strongly recommending practice under Okada’s personal guidance. It includes a dedicated section, “Precautions for the Magazine Quiet Sitting Faction”, outlining various problems that might arise for those practicing solely based on texts. However, in terms of fundamental principles, The Power of the Okada-style Quiet Sitting Method aligns with Three Years of Quiet Sitting regarding the approach to reverse breathing and concentrating strength in the abdomen.

The three figures discussed above were representative of the Japanese quiet sitting craze of their time. Their methods all exhibited a tendency to scientize and simplify traditional cultivation practices, emphasizing the interactive relationship between body and mind, possessing universal positive significance. Their techniques were emulated by a vast number of Japanese people, and many also wrote promotional works based on their personal insights. In these works, whether tracing theoretical origins or further elaborating on their experiences, individuals almost invariably mentioned Zen Master Hakuin. However, based on my limited reading, according only to the expressions in the relevant works, there were still some deviations between the Meiji-era Japanese cultivators mentioned above and Zen Master Hakuin in terms of cultivation techniques and tenets. The explanations are as follows:

First, many works concentrated their focus of cultivation solely on the abdomen where the dāntián is located, failing to emphasize the flow of energy throughout the entire lower body—dāntián, Sea of Qi, waist, feet, soles—as Hakuin did. The reason for this might be a misinterpretation of the concept of “Qi” in the Chinese context, limiting it to the qi of breathing. Since practitioners typically experience abdominal expansion and sensation during breathing, it seems as if qi is entering the abdomen. For instance, Futaki Kenzo directly understood Hakuin’s instruction to “direct the heart-qi down to the dāntián, Sea of Qi, waist, feet, and soles” as simply the “Method of Gathering Qi at the Dāntián and Sea of Qi”. Consequently, in their practical application, these practitioners did not adopt the series of self-inquiries advocated by Hakuin during mental concentration, such as, “My Sea of Qi, dāntián, waist, feet, and soles—all are my Original Face. What nostrils does this Face have?” Instead, they focused the practical operation on using the breath to create a sensation of the abdomen bulging, storing and applying force. This likely represents a one-sided understanding of Hakuin’s description of the abdomen becoming elastic “like an inflated leather ball” when Yuán Qi fills it. Japanese scholars frequently used terms like “abdominal pressure” and “concentrating strength in the abdomen” in their texts, guiding practitioners to exert force in the abdomen. Kishimoto even advocated wrapping a rope around the belly to train strength. However, as previously analyzed, Hakuin’s concept of “Yuán Qi filling the lower body” absolutely does not mean simply inhaling and holding breath in the abdomen. Furthermore, this kind of “abdominal strength” training method is never mentioned in Yasen kanna or related writings. In my opinion, this force-centric approach also contradicts the Daoist cultivation principle of “non-action and naturalness” (wúwéi zìrán 無為自然). Even in the preliminary, “action-oriented” (yǒuwéi 有為) stages, Daoism emphasizes “using intention, not force” (yòngyì bù yònglì 用意不用力) during the process of Guarding the One, advocating complete bodily relaxation. Although a sensation of tightness and strength in the lower abdomen may arise during mental concentration, this is merely a perception that need not be attended to; it is certainly not a state to be maintained through forceful effort. Excessive force can potentially lead to mental and psychological issues. Furthermore, when examined from the perspective of Daoist internal alchemy, Zen Master Hakuin’s method of using kōan such as “Original Face” and “Original Home” to guide practitioners in focusing their intention on the dāntián demonstrates considerable cultivation wisdom. This path aligns remarkably well with the essential principle of “concentrating the spirit on emptiness” (níngshén yú xū 凝神於虛) found in advanced alchemical methods. Chinese internal alchemists throughout history have also extensively elaborated on this. For example, Li Xiyue 李西月, the founder of the Western School of Daoism 道教西派, once said: “The Supreme Being takes emptiness as its foundation. Between the top and bottom, front and back, there is a circle of emptiness. If one can guard this, one’s breathing can penetrate deep into the dāntián.” 太上以虛無為本，上下前後之間，其中有一虛無圈子，人能守此，呼吸則能深入丹田。 (Xiyue Li 2009, p. 209). Similarly, Huang Yuanji 黃元吉 stated in his Leyutang Yulu 樂育堂語錄 (Recorded Sayings from the Hall of Delighting in Nurturing): “When learners begin practice, they must slightly close both eyes and clearly illuminate both the inner and outer dāntián, neither attaching nor separating, neither forgetting nor helping.” 學者下手興工，必將雙目微閉，了照內外二丹田之間，不即不離，勿忘勿助。 Professor Guo Guolong 戈國龍 annotates this in Dandao Jinquan 丹道今詮 (A Contemporary Interpretation of Daoist Internal Alchemy):

The Inner and Outer Dāntián: The Inner Dāntián refers to the dāntián within the body, which is the site for gathering the Internal Medicine. The Outer Dāntián refers to the dāntián outside the body, which is the site for gathering the External Medicine—that is, the formless realm of empty space. The Inner Dāntián is the root of conditioned life, while the Outer Dāntián is the root of primordial life. During alchemical refinement, one illuminates the dāntián with the light of the spirit (shénguāng 神光). However, one must not fixate on it rigidly; rather, one should maintain a posture of attentive yet non-grasping awareness, possessing the measure of emptiness. Hence, it is called “illuminating both the Inner and Outer Dāntián”. 內外二丹田：內丹田指身內丹田，為采內藥之處；外丹田指身外丹田，為采外藥之處，即是虛空無相之地。內丹田為後天生命之根，外丹田為先天生命之根。煉丹時以神光了照丹田，但不可死守，須似守非守，而有虛空之量，故曰了照內外二丹田之間。

(Ge 2013, p. 236)

Therefore, when we revisit Hakuin’s concepts of “Original Home” and “Pure Land”, they all bear a striking resemblance to the “Outer Dāntián”. Both aim to guide practitioners not to stagnate in the physical form nor be confined by the view of the body, thereby gradually transcending dualities such as inner/outer, self/other, and form/spirit, and returning to the original state of mind characterized by emptiness, tranquility, and non-attachment. In contrast, the understanding and articulation of these profound principles in various Meiji-era health practices seem less clear.

Second, when elaborating on their quiet sitting methods, the Meiji-era cultivators predominantly grounded their explanations in scientific rationality, consequently failing to sufficiently emphasize the underlying Buddhist or Daoist cosmological frameworks. However, it must be pointed out that quiet sitting, as a traditional method of physical and mental cultivation, has always been rooted in specific religious worldviews and understandings of life throughout its origin and development. The values inherent in Buddhist and Daoist thought—such as “impermanence” (wúcháng 無常), “emptiness and stillness” (xūjìng 虛靜), “guarding the mean” (shǒuzhōng 守中), and “non-attachment” (wúzhí 無執)—are directly manifested as key techniques for focused intent and breath regulation, exemplified by principles like “as if existing, as if not existing” (ruòcún ruòwáng 若存若亡), “neither forgetting nor helping” (wùwàng wùzhù 勿忘勿助), and “forgetting Spirit and Form” (wàngshén wàngxíng 忘神忘形). Regardless of the ultimate truth of the worldviews described by Buddhism and Daoism, based on the practical experience of Chinese practitioners, these fundamental concepts and key techniques provide crucial guidance for ensuring physical and mental safety during actual practice. Once these principles are deviated from, the more diligently a practitioner applies themselves, the more likely they are to induce physical and mental problems. This is precisely the fundamental reason why Hakuin devoted considerable space in Yasen kanna to explaining the Daoist cosmology.

Despite the limitations noted above, the cultivation practices represented by Kenzo Futaki, Fujita Reisai, and Torajirō Okada still played a positive role in promoting cultural transformation. By reinterpreting traditional cultivation methods through a scientific lens, they enhanced their acceptability in modern society. Coupled with the personal charisma of the three practitioners and the noticeable physical and mental effects of their methods, the related quiet sitting techniques gained widespread influence within Japanese society and were further transmitted to China, providing an important frame of reference and a resource for reflection for modern Chinese practices of physical and mental cultivation. The following section will discuss this further.

3.2. The Chinese Translation of Japanese Health Methods and the Formation of The Yinshizi’s Method of Quiet Sitting

In the early twentieth century, Japanese quiet sitting methods began to be introduced to China. Scholars such as Jiang Weiqiao 蔣維喬 (Yinshizi 因是子), Liu Renhang 劉仁航, and Lei Tongqun 雷通群 played a role in this dissemination, with the Commercial Press in Shanghai serving as the primary publishing platform. (X. Liu 2009) Between 1912 and 1919, the Commercial Press was committed to compiling and printing textbooks on self-cultivation to promote national education. Against this backdrop, Jiang Weiqiao and his friends translated and annotated several Japanese works on quiet sitting. For instance, the works of Fujita Reisai were translated by Liu Renhang and proofread by Jiang Weiqiao, published successively as Method of Harmonizing Body and Mind (身心調和法, 1916) and Secrets of Physical and Mental Strength and Health (身心強健祕訣, 1917). In 1913, the Eastern Miscellany 東方雜誌, published by the Commercial Press, featured an article introducing the Okada-style Quiet Sitting Method. By 1919, the Okada-style Quiet Sitting Method, translated by Wu Yinzhai 吴寅齋 and polished by Jiang Weiqiao, was formally published. Additionally, Hua Wenqi’s 華文琪 translation of Three Years of Quiet Sitting was completed in 1916, and Lei Tongqun’s translation of The Psychology of the Okada-style Quiet Sitting Method 岡田式靜坐心理 was completed in 1920. A brief commentary on their content follows (X. Chen 2023).

Liu Renhang once studied in Japan, where he learned from Fujita Reisai. Well-versed in both Buddhist and Daoist doctrines himself, Liu’s annotations often supplement Fujita’s experience-based descriptions. He cited Chinese classics to clarify the underlying principles, thereby revealing the commonalities among practitioners of different sects. For instance, in response to Fujita’s suggestion in the “abdominal reading method”—“a circle can be used to represent a kōan, and choosing the image of a bright moon is also excellent. Practicing under the full moon on the fifteenth day of the lunar month is especially wonderful, as if one feels the moonlight illuminating the dāntián; following this method yields particularly good progress”—Liu added an annotation stating: “This method that are directly aligned with the Zhouyi and Buddhist teachings. Without understanding the principles of Buddhism and the Zhouyi, one cannot fully grasp its profundity. In the Zhouyi, the Kǎn trigram (坎☵) symbolizes the moon…” (R. Liu 1917, p. 148). Such annotations are frequently found in his translations. Liu also cautioned against potential deviations in practice within his annotations. For example, he pointed out: “If practitioners are not skilled and the breath is used too hastily, mild cases may lead to illness, while severe cases could result in fainting or breath suspension. Although it may not be fatal, such risks should still be considered. If self-practice proves unsuitable, learning under a master would be a more secure approach.” (R. Liu 1917, pp. 138–139).

However, the influence of Liu’s translation and annotation of Fujita’s works in China at that time was not as significant as that of The Okada-style Method of Quiet Sitting. The reason for this may be related to Jiang Weiqiao. Inspired by the popularity of various Japanese works on quiet sitting, Jiang Weiqiao drew on his own long-term practice to write The Yinshizi’s Method of Quiet Sitting, which gained widespread circulation in China. In the preface, he explicitly stated: “Recently, I have learned that both Okada Torajirō and Fujita Reisai of Japan have been advocating methods of quiet sitting, each attracting tens of thousands of followers. Okada’s disciples compiled The Okada-style Method of Quiet Sitting, while Fujita authored two books—Method of Harmonizing Body and Mind and Secrets of Physical and Mental Strength and Health—which enjoyed immense popularity and were reprinted dozens of times. After reading them, I exclaimed with emotion: ‘This is clearly a cultivation method that our country has had since ancient times!’ The works of Okada and Fujita explain principles in a plain and practical manner, avoiding mystical speculation. What distinguishes them from our ancient texts is that their theories are grounded in modern sciences, philosophy and other disciplines.” (Jiang 2011a, p. 3). In The Yinshizi’s Method of Quiet Sitting, Jiang Weiqiao adopted certain terminology and expressions from Japanese books on quiet sitting. When introducing breathing methods in his book, Jiang also incorporated Okada’s theory and adopted the method of reverse breathing. He also appended The Okada-style Method of Quiet Sitting to his own work for readers’ reference.

However, there were fundamental differences between Jiang Weiqiao’s Method of Quiet Sitting and Okada’s Method. He astutely identified potential practical issues in the methods compiled by Okada’s disciples. For instance, in his preface to Lei Tongqun’s The Psychology of Okada-style Quiet Sitting, he pointed out: “Okada himself emphasized personal instruction and did not author any works initially. It was his disciples who later compiled The Okada-style Method of Quiet Sitting based on their understanding. Among these, Kishimoto’s Three Years of Quiet Sitting is relatively detailed, yet its emphasis on forcibly distending the abdomen appears prone to undesirable consequences.” (Lei 1920, p. 1). In terms of technique, Jiang’s method adhered to the traditional Daoist cultivation practices of China. Although he actively introduced Japanese innovations, he cautioned readers against blind imitation, explicitly advising: “The sitting postures described in The Okada-style Method of Quiet Sitting follow Japanese customs. Readers should not force themselves to emulate these but may adapt them to Chinese habits. For reference, please consult my work The Yinshizi’s Method of Quiet Sitting.” Jiang’s approach placed greater emphasis on the Daoist tenet of “following natural law” (dàofǎ zìrán 道法自然). Notable distinctions between his method and the Okada-style include the following aspects:

First, regarding breathing rhythm, Okada advocates for slow exhalation but fast inhalation, whereas Jiang Weiqiao emphasized that inhalation should also be gentle and gradual, aiming to gradually reach a state where breathing becomes “as if existent yet non-existent” (ruòcún ruòwáng 若存若亡).

Second, in terms of abdominal focus, Okada emphasized “concentrating strength in the abdomen”, while Jiang opposed deliberate breath-holding or exertion. He noted: “Stabilizing the lower abdomen helps anchor the body’s center of gravity, but this does not mean exerting force intentionally. Rather, through the function of mind intent, one eliminates distracting thoughts and concentrates attention downward, allowing the center of gravity to stabilize naturally.”

Third, Jiang placed greater emphasis on mental adjustment during practice, advocating: “While quiet sitting can eliminate illness and enhance health, the very thoughts of seeking healing or fitness should also be discarded. One must act in total accordance with nature, without striving for quick results—like a leaf boat drifting mid-stream, abandoning oars and sails, letting it go where it will.”

Fourth, Jiang selectively integrated key techniques from Daoist practice. For example, he emphasized that during sitting, “the mouth should be closed, with the tongue touching the upper palate” 口宜噤，舌抵上齶—a Daoist method known as “building the magpie bridge” (dā quèqiáo 搭鵲橋), intended to connect the Rèn and Dū meridians 任督二脈 (Conception and Governor Vessels). Regarding possible bodily vibrations during sitting, Jiang further elaborated a method, guiding thermal energy with the mind along the spine and through the Rèn and Dū meridians: “When vibration occurs, use intent—without exertion—to guide this dynamic force from the coccyx (wěilǘ 尾閭), up along the spine to the neck, passing over the crown, then descending gently through the face to the chest center and down below the navel. With sustained practice, this force will naturally circulate upward and downward, and can be directed throughout the body, permeating every part—even to the tips of the nails and hair. At this stage, the whole body grows warm, and an extraordinary sense of well-being arises.” In fact, this is a Daoist cultivation method known as “circulating the Microcosmic Orbit” (xiǎo zhōutiān 小周天, involving the circulation of qi through the governor and conception vessels). In comparison, although later practitioners of the Okada method also experienced bodily vibrations, they had not yet developed a systematic theory of energy circulation comparable to Jiang’s (Jiang 2011a, p. 3).

Interestingly, in his book The Sequel to Yinshizi’s Method of Quiet Sitting, 因是子靜坐法續篇 published a few years later, Jiang Weiqiao showed a clear shift in his thinking, explicitly abandoning cultivation methods with Daoist colors and instead embraced the Buddhist practice system. The entire book replaced the original practice of “concentrating the mind on the dāntián” with the Buddhist method of “cessation-and-contemplation”, and significantly increased content on mental nature cultivation and dealing with desires, emphasizing that only the Buddhist Dharma could achieve the fundamental settling of life. The motivation for this shift partly stemmed from the widespread social influence following the publication of The Yinshizi’s Method of Quiet Sitting and the ensuing practice problems. Jiang Weiqiao explained in the sequel: “After the first volume was published, sales reached several tens of thousands of copies. There were many learners, and letters questioning and doubting came in an endless stream, from nearby provinces to distant overseas, almost everywhere had people practicing. I am struggling to inform everyone of my experiences of the past few years one by one, so I had to use writing to convey the thoughts of recent years.” Simultaneously, he also noticed that many practitioners developed deviations due to attachment to bodily sensations and states, pointing out: “Those who cultivate this path today often like to talk about various miraculous states within concentration. Learners, tempted by this, suffer no small harm.” And he emphasized: “learners should know that Quiet Sitting is absolutely not about seeking miracles. Even if one indeed encounters miracles, one should abandon them, must not grasp them, lest one fall into demonic states.” (Jiang 2011b, p. 5).

Jiang Weiqiao himself possessed a solid foundation for study and practice. According to his own account: “My father perceived the source of my illness and sometimes showed me books on cultivating mind and nature, and also showed me the Daoist methods of circulating the Microcosmic Orbit recorded in traditional Chinese medicine books.” (Jiang 2011a, p. 63). This family learning and mental nature cultivation allowed him to avoid “demonic states” during his long-term quiet sitting practice. However, this might also have led to an insufficient awareness of individual differences. Therefore, in the first volume, Jiang shared his detailed personal insights on quiet sitting with an open attitude, intending to provide reference for readers. However, cases in the sequel revealed that many practitioners with limited cultural literacy easily developed attachment to bodily sensations, pursued special experiences, and, coupled with differences in individual physical and mental states, were prone to hallucinations. For example, the sequel records a practitioner who “practiced for several years with quite good results. Suddenly one evening, during stillness, he saw many naked women surrounding him and making noise. The gentleman was greatly alarmed, urgently concentrated his mind, remained unmoved, but the demons did not retreat. He was then greatly astonished” (Jiang 2011b, p. 63).

Based on these practical considerations, Jiang Weiqiao not only repeatedly emphasized non-attachment to any physical or mental sensations and states but also introduced in his sequel a specific method of reciting “Namo Amituofo” 南無阿彌陀佛 to counteract adverse spiritual states. He advised practitioners to establish firm faith in Amitabha Buddha and to deeply believe in the reality of rebirth in the Western Pure Land 西方極樂世界 (Sukhāvatī). To this end, he specially appended a section titled “Essentials of Buddhism” at the end of the sequel, systematically elaborating on the fundamental tenets of Buddhism. These adjustments demonstrate that, driven by profound concern for practitioners’ physical and mental safety as well as their ultimate spiritual destiny, Jiang consciously redirected the practice of quiet sitting toward the correct view of the Buddhist Dharma. In this respect, his pedagogical approach shares notable intrinsic commonalities with the spirit of Hakuin Ekaku.

3.3. The Scrutiny and Correction of the Drawbacks of Quiet Sitting Methods by Chinese Cultivation Masters

Although Jiang Weiqiao had shifted to the Buddhist system of practice in his Sequel, the first work, due to its straightforward methods and ease of practice, coupled with Jiang’s own repeated personal testimonies of remarkable efficacy and vivid descriptions of revitalized states of life, continued to inspire many later practitioners to engage in similar quiet sitting practices. Against this backdrop, Chinese intellectual circles gradually became aware of the potential drawbacks involved and consequently sought to provide more comprehensive interpretations of quiet sitting. This aimed to promote a more accurate public understanding of traditional Chinese cultivation culture, thereby truly benefiting both body and mind.

Chen Yingning 陳攖寧 (1880–1969), a pivotal figure in modern Chinese Daoism, broke with the tradition of secrecy surrounding Daoist practices by vigorously advocating for the demystified study of “Immortal Studies” (xiānxué 仙學). He authored the Q&A column for the Yangshan Bimonthly 揚善半月刊, publicly sharing his own cultivation experiences and gathering numerous Daoist enthusiasts, making the publication a key national platform for Daoist academic exchange (Palmer and Liu 2012). It also contains several instances where Chen responded to readers’ problems regarding their practice of the Okada-style method. For example, in his “Reply to a Letter from a Gentleman at South Chezhan Station, Shanghai” 答復上海南車站某君來函 (1936), he stated: “This gentleman’s problem lies in forced effort and artificiality, which contradicts the principle of naturalness… There is no need to manipulate the breath during quiet sitting—such effort only adds to the distress. It must be understood that what Daoism calls ‘true breath’ (zhēnxī 真息) involves different manifestations and subtleties, and is certainly not the same as the reverse breathing method of Japan’s Okada. Okada himself did not achieve success, falling ill and dying prematurely; how then can Chinese people peddling foreign goods expect good results?” (Guo 2014, p. 169).

Grounded in the core Daoist tenet of “following natural law”, Chen pinpointed the root cause as forced effort and artificiality, contradicting the principle of naturalness. He pointedly noted Okada’s early death as a warning against the blind application of foreign methods. Another response regarding the drawbacks of the Okada method appears in “A Reply to the Carefree Mountain Hermit of Baiyun Temple” 答白雲觀逍遙山人 (1937): “Cases of ‘semen leakage’ (zǒudān 走丹) during the practice of the Microcosmic Orbit are not uncommon. The cause often lies in excessive sleep, or rigidly concentrating on the lower dāntián, accumulating essence excessively without knowing how to transform and circulate it. As for cases where quiet sitting practice leads to spitting blood, these are quite rare. However, among those who studied the Japanese Okada-style method, there were occasional instances of hemoptysis. The drawback stemmed from excessive force in reverse breathing, leading to ruptured blood vessels. The Daodejing 道德經 says: ‘Reach the utmost emptiness, hold fast to profound tranquility.’ This passage of scripture must be carefully studied. When people in the world engage in practice and end up with serious illnesses, it falls under what the scripture describes as ‘Not knowing the constant, one acts recklessly, leading to misfortune’. 不知常，妄作兇。” (Guo 2014, p. 308).

Chen’s response here directly addresses the issue of “using force” discussed earlier by the author and also mentions a potential error in quiet sitting practice—rigidly fixating on the lower dāntián. Regarding this point, I have some personal experience. In my twenties, I attempted quiet sitting and concentrating on the cavity based on The Yinshizi’s Method of Quiet Sitting. I quickly felt warmth in my dāntián, as if qi was gathering. However, having neglected Jiang’s advice regarding mental cultivation, lacking sufficient humanistic grounding, and without a teacher’s guidance, I persistently focused on the lower dāntián with an impatient mindset. This repeatedly led to increased sexual desire and even nocturnal emissions during sleep, particularly after heavy meals or consuming rich, greasy food. This seemed to resonate with Chen Yingning’s observation of “accumulating essence excessively without knowing how to transform and circulate it”. This raises a question worthy of further exploration: since there are no descriptions of exercises like the Microcosmic Orbit in Yasen kanna, was the “Soft Butter Method” specifically mentioned by Hakuin designed to alleviate such issues? Hakuin does not explicitly state this in his text. Although I lack direct personal experience, I have found similar descriptions in Daoist texts, and therefore quote them here for reference. The section on the “Dāntián” in Danjing Jilun 丹經極論 (Elucidations on the Classic of Internal Alchemy) states:

In your practice of internal alchemy, you may suddenly feel a surge of energy ascend directly from the Jiájǐ point 夾脊 to the Mud Pill Palace (níwán gōng 泥丸宮), accompanied by a faint, trickling sound. It will seem as if something at the crown of your head touches the upper brain. Shortly, this substance—taking a form about the size of a sparrow’s egg—will descend one after another from your palate, flowing slowly down along the “Multi-storied tower” (chónglóu 重樓, a term symbolizing the throat with its twelve vertebrae). Its taste is akin to chilled butter—fragrant, sweet, delicious, and beyond compare… You should then slowly and continuously swallow and guide it back to your dāntián. Your five zang-organs will feel clear and cool. Close your eyes, turn your vision inward, and you will see the internal organs distinctly, as if illuminated by candlelight. Gradually, ten thousand rays of golden light will begin to shine forth and penetrate your entire body. 運丹生成之際，忽覺夾脊上沖泥丸，瀝瀝有聲，從頭似有物觸上腦，須臾如雀卵，顆顆自愕下重樓，如冰酥香甜，甘美之味無比。覺有此狀，乃得金液還丹。徐徐咽歸丹田不絕。五臟清凍，閉目內觀，藏府歷歷如照燭，漸次有萬道金光透體也。

(Danjing Jilun 丹經極論 1988, p. 347)

This passage describes part of the sensory experience reported by an internal alchemy practitioner, sharing similarities with Jiang Weiqiao’s earlier accounts. The imagery and sensation of “ice butter, sweet and fragrant, descending from above” bears a remarkable resemblance to the imagined process in Hakuin’s “Soft Butter Method”. Therefore, based on the perspective of this article, one possible intention behind Hakuin’s introduction of auxiliary methods like the Soft Butter Method might have been to subtly guide practitioners, in an “unintentional” manner, to unconsciously circulate and transform energy, thereby resolving issues like qi stagnation that can arise from rigidly focusing on specific points. However, Hakuin did not explicitly point out the connection between this practice and methods such as Guarding the One and regulating breath during cultivation. I think this might be because clearly explaining that this sensation would occur after practicing could easily lead practitioners to anticipate and imagine this feeling, thereby strengthening their attachment to bodily sensations, deviating from the original intention of Zen, and potentially causing physical and mental problems. This issue still requires further empirical research and analysis by experienced practitioners.

My reflection on this issue was inspired by the writings of Mr. Nan Huaijin 南懷瑾. Because Jiang Weiqiao described several of his own extraordinary experiences in his book, after which his various illnesses were completely cured, this inadvertently fostered attachments among many practitioners. Mr. Nan Huaijin’s series of works were, to a considerable extent, aimed precisely at correcting such deviations. He sternly pointed out: “When people sit in meditation and feel the Qi activating within the body, the most common mistake is to unconsciously fix their attention on these sensations. This focus intensifies, until the entire mind disturbs the vital energy, creating illusions, associations, and other forms of deranged mentality. Those slightly better off believe their channels have been cleared and become smug. In reality, the true phenomena of opened channels are not like this. For the worse cases, due to their perception of energy flow, tend to concentrate excessively, which, unconsciously combined with conscious fantasies and other psychological processes, leads to excessive nervous tension. This becomes what is generally called ‘demonic states’. It is not that quiet sitting causes one to be possessed by demons; rather, it is the demon of a distorted mentality, arising from not understanding the true principles of quiet sitting, that harms the serene state sought in the practice!” (Nan 2003, p. 520).

Mr. Nan Huaijin, a master integrating the teachings of Confucianism, Buddhism, and Daoism. He once stated frankly that one of the purposes of his book Sitting Meditation and Immortality 靜坐修道與長生不老 was to dispel the contemporary obsession with methods like the Yinshizi’s Method and the Okada-style Method. He scientifically explained the various physical sensations that can arise from “focusing the mind on one point” during sitting from the perspective of mind–body interaction, pointing out that these feelings are often related to mental guidance and physiological responses. Nan’s discourse is full of profound insights. For instance, he noted that the quiet sitting method of focusing the mind on the dāntián is not suitable for everyone and requires consideration of individual physical and mental differences. He analyzed that Jiang Weiqiao’s success was also due to his originally severe illness and weak constitution, which conversely made it easier for his mind to become clear and empty. Consider Japan’s Hakuin, Fujita, and Futaki—there are also records of them recovering from serious illnesses through cultivation. Nan’s warnings regarding health issues were particularly pertinent. For example, he pointed out that women focusing on the dāntián might cause excessive menstrual bleeding, a conclusion drawn from the accumulated experience of female Daoist practitioners throughout Chinese history, hence the existence of specific methods for women’s practice. Furthermore, he criticized certain Buddhist practitioners who sat all night counting breaths, mistaking the method for the goal itself, emphasizing the need to shift from “counting breaths” (shǔxī 數息) to “following the breath” (suíxī 隨息) to achieve a higher level of physical and mental tranquility. His writings are extensive yet accessible, aiming to point the public toward a safe path of practice. This guiding spirit shares common ground with Zen Master Hakuin’s original intention of benefiting sentient beings through skillful means. Although Nan Huai-chin had no direct lineage connection with Hakuin, both were esteemed Buddhist figures with deep practical experience and wisdom, their thoughts inherently aligned at the fundamental level. The author believes that Nan Huaijin’s relevant discussions can serve as an excellent frame of reference for deeply understanding Hakuin’s practice methods that incorporated Daoist elements, and for apprehending the underlying intention and wisdom of his teachings.

In fact, methods of quiet sitting, breathing, and respiration have been practiced in China for thousands of years, their principles and techniques profound and extensive. As Liu Renyang stated, the Japanese quiet sitting methods of Fujita and others “can be summarily concluded as not exceeding the Huang-Lao teachings 黃老之學 (Huangdi 黃帝 and Laozi, the founders of Daoism) of our country” (R. Liu 1917, p. 95). The path of quiet sitting is one where a minute deviation can lead to a huge error; Chinese Daoist practitioners have accumulated a wealth of insights into its mysteries. However, as Jiang Weiqiao pointed out, Daoist texts are often abstruse, lack clear operational guidance, and emphasize oral transmission from master to disciple, not being readily disclosed, making truly safe practice methods difficult to popularize. In this sense, although Japanese quiet sitting methods occasionally produced drawbacks during their dissemination, their scientific explanations and universal promotion strategies indeed provided an important reference for the modern transformation of traditional Chinese cultivation culture. This cross-cultural exchange and collision stimulated Chinese practitioners to gradually disclose some secretly transmitted essential methods, enabling the general public to access more systematic and safer practice approaches—and this, perhaps, was the foresight embodied in Zen Master Hakuin’s original integration of Daoism and Zen for the universal benefit of all beings.

4. Conclusions

Through close reading and conceptual analysis, this study elucidates how Hakuin Ekaku absorbed and transformed theories and practices from Chinese Daoist internal alchemy into his Zen system, tracing the subsequent transmission, adaptation, and cultural reverberations of this syncretic practice.

Regarding the specific content and distinctive features of Hakuin’s synthesis, this study demonstrates its systematic yet selective nature. Primarily through the narrative persona of the immortal Hakuyūshi in Yasen Kanna, Hakuin introduced a Daoist worldview of life and the body. Its core is the cosmology of “correspondence between heaven and humanity”, which regards the human body as a microcosm operating through the dynamics of vital energy. From this perspective, he diagnosed “Zen sickness” as stemming from the adverse rising of heart-fire and the disruption of the heart–kidney interaction. The Daoist methods he adopted—such as Guarding the One and Fetal Breathing—aimed to guide the heart-fire downward, nurture Yuán Qi, and thereby harmonize body and mind to stabilize the foundation for Zen practice. His theoretical articulations also clearly absorbed internal alchemy thought from the Southern School of Daoism, as seen in formulas like “when the Spirit is concentrated, Qi gathers”, reflecting a considerable systematic understanding.

However, Hakuin’s integration was marked by a distinct Zen subjectivity and practical orientation. He did not pursue the ultimate Daoist goal of forging the golden elixir but selectively adopted techniques effective for curing Zen sickness, strengthening the physical body, and aiding mental concentration. Crucially, his insight into advanced stages of Daoist cultivation, such as the state associated with the Primordial Unity of Qi, enabled him to profoundly transform these methods operationally. For instance, when teaching mind concentration on the dāntián, he skillfully converted the act of fixing attention into investigating kōan such as “Original Face” or “Original Home”. This embedded the simple process of psychosomatic regulation within the dynamic tension of Zen inquiry. It thus turned moments of bodily sensation into opportunities to sever the view of a real self and realize one’s true nature. This design of “simultaneous regulation and investigation” ensured that health-nurturing work consistently pointed toward the Zen goal of illuminating the mind and seeing one’s true nature, showcasing his profound wisdom and skillful means as a Zen master.

Furthermore, this syncretic practice initiated a cultural flow across religious, regional, and temporal boundaries. As detailed in this paper, from the Meiji period onward in Japan, Hakuin’s health-preservation methods were divorced from their original religious context, reinterpreted, and popularized under names like “abdominal breathing method” and “quiet sitting method”, often explained through modern physiological knowledge. Subsequently, these Japanese-style methods flowed back to China in the early twentieth century, stimulating the creation of indigenous works like Jiang Weiqiao’s The Yinshizi’s Method of Quiet Sitting and prompting reflection and correction of potential drawbacks in sitting meditation within Chinese cultivation circles. This process of adaptation in Japan and subsequent reinterpretation in China demonstrates not only the enduring vitality of Daoist health-preservation wisdom during East Asia’s modernization but also reveals common tendencies of popularization and scientification in cross-cultural knowledge transmission, along with their inherent adaptations.

Finally, building on this study’s findings, future research could explore several promising directions. One avenue is to further contextualize Hakuin’s intellectual motivations by examining them against the broader backdrop of Sino-Japanese Buddhist exchange during the Edo period. Another is to extend the investigation of cross-cultural impact by situating the modern circulation of his methods within the macro perspective of East–West encounter, exploring how his system acted as a “mediator” between traditional somatic knowledge and modern science. Furthermore, constructive dialogue could be fostered between this Eastern psychosomatic tradition and modern disciplines such as psychology, psychosomatic medicine, and comparative religious studies, offering richer cross-cultural resources for contemporary holistic well-being.

This study has preliminarily clarified the content, logic, and cross-cultural trajectory of Hakuin’s “incorporating Daoist practices into Zen”. However, the assessment of its details, particularly the deeper implications and limitations of certain practical methods, still awaits further examination and refinement by more practitioners with empirical experience and scholars from interdisciplinary fields. This path of self-cultivation, traversing Zen, Daoism, and medicine and flowing between China and Japan, provides a vivid and profound case for understanding the complexity of cultural fusion in East Asia and the modern transformation of traditional wisdom.