Hakuin Ekaku 白隱慧鶴 (Jōkyō 2 / 1686-01-19 → Meiwa 5 / 1769-01-18 — 12 / 11 Meiwa 5 OS), the single most consequential Rinzai-Zen master of the Edo period and the architect of the modern Japanese Rinzai-Zen curriculum. Style-name (字) Hakuin 白隠 (“White Hidden”); dharma-name Ekaku 慧鶴 (“Wisdom Crane”); pagoda-name Kakurin 鵠林 (“Goose Grove”). Posthumous title Shinki Dokumyō Zenji 神機獨妙禪師, with the later additional title Shōshū Kokushi 正宗國師 conferred at the 100-year memorial in 1868. Native of Hara 原 village in Suruga 駿河 province (modern Numazu, Shizuoka).
Tonsured young at Shōin-ji 松蔭寺 in his native village; trained widely; received transmission from Shōju Rōjin Etan 正受老人慧端 (1642–1721) in the Inzan / Myōshin-ji-Reiun-ha line. Returning to Shōin-ji aged 31, Hakuin spent the remaining four decades of his life there, developing and disseminating the kōan curriculum that came to dominate Japanese Rinzai-Zen — beginning with his celebrated Mu and one-hand-clapping (隻手の音聲 / Sekishu no onjō) introductory kōan and progressing through jakugo (capping-phrase) practice on the Bìyánlù, Wúménguān, Xū-tang-roku, and the recorded sayings of 妙超 Daitō Kokushi.
Hakuin’s principal heirs Tōrei Enji 東嶺圓慈 圓慈 (1721–1792) and Gasan Jitō 峩山慈棹 (1727–1797) — the Two Pillars (Ryōchū 兩柱) — institutionalised his curriculum at Ryūtaku-ji and Enpuku-ji respectively, and every present-day Japanese Rinzai-Zen training-line descends through one of them. Hakuin is also notable for his paintings and calligraphy (an extensive corpus of Zen brushwork survives), and for Yasen kanwa 夜船閑話 (“Idle Talk on a Night Boat”), the naikan meditation-therapy text. His major Zen-literary works are Sokkō-roku kaien fusetsu 息耕録開筵普説 (commentary on the Xū-tang yulu), Itsumadegusa 邊鄙以知吾 (autobiography), and the Kaiankoku-go 槐安國語 (the present text KR6t0280) — his great commentary on Daitō Kokushi’s recorded sayings.