Lü Dongbin's Secret of the Golden Flower chapter, "The Union of Kan and Li," explains alchemical self-cultivation using the trigrams Kan and Li. Kan represents inward focus and stillness, while Li represents outward engagement. The text equates the union of these forces with the harmonization of yin and yang, body and mind, and ultimately, spirit and vital energy (qi). Achieving this union, even through simple breath control, is described as a crucial step on the path to spiritual attainment, with meditation representing an advanced stage.