Chén Tuán 陳摶 (hào Xīyí 希夷先生, courtesy name Tú’nán 圖南 and Fúyáo zǐ 扶搖子; d. 989) was a Five-Dynasties / early-Sòng Daoist recluse and cosmologist, celebrated in later tradition as the foundational ancestor of Sòng nèidān 內丹 (“inner alchemy”) and of the Hétú 河圖 / Luòshū 洛書 diagrammatic tradition that culminates, by separate lineages, in the cosmologies of Shào Yōng 邵雍 and Zhū Xī 朱熹. He refused office under both the HòuZhōu 後周 and the early Sòng, retiring in later life to Mount Huà 華山, where he is said by his Sòngshǐ biography (457.13421) to have practiced extreme dormancy and breathing exercises and to have composed a Zhǐxuán piān 指玄篇 on “gymnastics, nourishing the vital principle, and the cyclically-transformed elixir.” Many works of the early Northern Sòng were pseudepigraphically attached to his name, so that the authorship of most of the texts that now survive under his name is uncertain. CBDB gives birthdate unknown and death in 989. In the Kanripo corpus he is attributed as commentator of [[KR5a0135|KR5a0135 Yīn zhēnjūn huándān gē zhù]] and of other commentaries; his larger lineage shapes the cosmology of numerous Shào Yōng–school Yìjīng works in KR1 as well.