Secret Essentials of the Five Categories 参同契五相类秘要

Compiled by Lu Tianji of the Northern Song Dynasty.

Consisting of one volume, it is included in the Methods category of the Dongshen Section in The Daozang.

This book expounds on the methods of subduing mineral medicines in external alchemy, rooted in the theoretical system of Taoism. It first interprets the essential purport of Wei Boyang’s Five Complementary Categories in Cantong Qi. It declares: "The Five Complementary Categories discuss the subduing of the Three Yellows and Two Treasures through compatible substances." The Three Yellows refer to realgar, orpiment and sulfur; the Two Treasures denote lead and mercury—all are metal-mineral medicines for refining the Great Elixir of Return.

During the alchemical process, it is necessary to use compatible medicines for coordination and subduing, then imitate the trigrams of the Bagua and control the firing temperature to refine the golden elixir. Therefore, the book lists thirteen types of compatible medicines, with notes on the methods of subduing mineral medicines. For instance, it states: "Realgar is compatible with cinnabar"; "Orpiment is compatible with honey water and fritillaria, turning into liquid instantly when exposed to fire"; "Cinnabar is compatible with pure vinegar"; "Lead is compatible with mulberry ash and dead souls"; "Kunlun (azurite) is compatible with goat fat", and so on. Only by understanding and applying the compatibility and subduing properties of these mineral medicines can one successfully refine the elixir.