Cuī Xīfàn 崔希範 (also Cuī Xuánzhēn 崔玄真, with Daoist title Zhìyī zhēnrén 至一真人 — sources conflate the two names) is a Táng alchemical poet attached in tradition to Mínshān 岷山 (Sichuan). Xīn Tángshū “Yìwén zhì” dates him to the Tiānbǎo era (742–756). He is conventionally credited with authorship of the Rùyào jìng 入藥鏡, a terse poem of alchemical formulas that circulates in several very different versions (Táng five-character Jīnbì qiántōng rùyào huǒjìng jí; a three-character version glossed in DZ 135; a Tiānyuán rùyào jìng linked to Lǚ Dòngbīn 呂洞賓 and dated 940; a Buddhist-flavored Shàngpiān in [[KR5c1017|DZ 1017 Dàoshū]] 37; see Schipper & Verellen eds., The Taoist Canon [2004] 2:843–844). In later nèidān tradition Lǚ Dòngbīn’s biography at [[KR5c0296|DZ 296 Lìshì zhēnxiān tǐdào tōngjiàn]] 45.2b has Lǚ receiving the Rùyào jìng from Cuī gōng in 881, which is chronologically implausible but testifies to the centrality of Cuī in the nèidān transmission lineage.