The Secret Instructions for the Dragon-Tiger Middle Elixir 龙虎中丹诀

The author is unknown. Judging from its content and wording, it was presumably composed by a Taoist priest during the Song Dynasty.

Consisting of one scroll, it is included in the Methods Category of the The Dongzhen Section within the Taoist Canon (The Daozang).

The Secret Instructions for the Dragon-Tiger Middle Elixir

This text expounds the secret practices of Internal Alchemy (Neidan). It contains six eulogistic poems (Ode to the Functions of Dragon and Tiger, Ode to Embryonic Yang, Ode to the Embryonic Chamber, Ode to the Embryonic Spirit, Ode to the Embryonic Intelligence, Ode to Embryonic Transformation), three mantras (True Fire Mantra, True Water Mantra, Fire Cultivation Mantra), three trigram diagrams (Circadian Cycle Diagram, Fu Gua Diagram, Gou Gua Diagram), and nine seven-character regulated poems (titled "Nine Stages of the Water-Fire Middle Elixir").

Its alchemical method generally holds that essence, Qi (Vital Energy), and spirit are the masters of the human body—only the mind can initiate their integration and transformation. The sun and moon are the purest essence of heaven and earth, while Kan ☵ and Li ☲ (trigrams representing water and fire) are the supreme medicines within the human body. By enabling Kan and Li to unite the sun and moon in the Mysterious Palace (Xuangong), the True Elixir is formed. It further states that elixir refinement must be practiced before midnight and after noon: following the sequence from Fu Gua ☳ to Qian Gua ☰, and concluding from Gou Gua ☱ to Kun Gua ☷. After nine years of practice, the elixir matures, the embryo transforms, and one returns to the root and reverts to the primal state—thus becoming a true immortal.