Neidan Dictionary
wu tu 烏兔
crow and hare
※ These two images derive from an early Chinese myth, according to which a crow (Yin) lives in the Sun (Yang), and a hare (Yang) lives in the Moon (Yin).
① The ingredients of the Elixir. The Crow represents Mercury (True Yin) and the Hare represents Lead (True Yang).
⊛ First take Qian and Kun as the tripod and the furnace, then catch the Crow and the Hare and boil the Medicine. 先把乾坤為鼎器,次搏烏兔藥來烹。 (Awakening to Reality, "Cut-off Lines", poem 1, trans. in Taoist Internal Alchemy: An Anthology of Neidan Texts, p. 77)
⊛ The Yang Breath pertains to Li ☲, and the Yin Essence pertains to Kan ☵. Therefore we speak of the Crow and the Hare as the ingredients. (Four Hundred Words on the Golden Elixir, Preface)
⊛ Take Qian ☰ and Kun ☷ as the Tripod and the Furnace; the Sun and the Moon as Water and Fire; Yin and Yang as the mechanism of transformation; and the Crow and the Hare as the ingredients. 以乾坤為鼎器,日月為水火,陰陽為化機,烏兔為藥物。 (Li Daochun, The Harmony of the Center: An Anthology, chap. 3)