Nine Essentials of the Heart-Mind Seal 太上九要心印妙经

Originally attributed to "the Immortal Zhang Guolao as narrated".

It is not recorded in any bibliographic records of the Tang and Song dynasties, and is presumably a work falsely attributed by Taoist priests in the late Tang and Northern Song dynasties.

Comprising one scroll, it is included in the Methods category of the Dongzhen Section of The Daozang.

The entire text is divided into nine treatises expounding the essential secrets of Internal Alchemy cultivation. The treatises are titled: The Essential Secret of the True One, The Essential Secret of the Bellows, The Pivotal Essential of the Three, Five and One, The Fundamental Essential of the Three and One, The True Essential of the Sun's Soul and Moon's Essence, The Profound Essential of the Five Elements in Daily Practice, The Concise Essential of the Seven Reversions to the Elixir, The Unifying Essential of the Eight Trigrams Paying Homage to the Origin, and The General Essential of the Nine Reversions to the Single Qi.

Its doctrines generally take nature and life as the guiding principle, and essence, spirit and Qi as the medicinal ingredients for cultivation. It holds that spirit and Qi are the lead and mercury within the human body: regulating Qi with spirit, calming spirit with Qi, embracing spirit and Qi in mutual unity, consolidating nature and life in interdependence, merging them into a single flow of Qi, and thereby generating the true fire. Refining one’s essence back with this true fire, transforming essence into spirit, uniting spirit with the Dao, and returning to the state of nature—this is the core of the alchemical way.

It further classifies alchemical methods into three types: the method of immortals embracing the One, refining the spirit and uniting with the Dao; the method of nurturing Qi to enrich the nation and secure the people’s peace; and the method of strengthening troops to secure victory, based on the intermingling of the dragon and tiger. It also divides the Great Elixir into internal and external elixirs: the external elixir is the Qi of the five grains, and the internal elixir is the Qi of the True One. It holds that "the internal elixir cannot be accomplished without the external elixir, and the external elixir has no foundation without the internal elixir".