Small Reversion Elixir
In parallel with the Great Reversion Elixir ( 大還丹 Xiaohuan Dan ), the Small Reversion Elixir was also popularly used in books on Inner Alchemy ( 內丹 Neidan ). In these books, it used to stand for the mixture of Kidney Water ( 腎水 Shenshui ) and Mind Fire ( 心火 Xinhuo ), or the mating between Yin ( 陰 Yin ) and Yang ( 陽 Yang ), in another term. According to the Trigram Figures from the Book of Changes ( 易 Yi ), one Hexagrammatic Line standing for Yang ought to be taken from Kan, and one Hexagrammatic Line standing for Yin added to Li. In this way, the Trigram Figures of Kan and Li return to those of Qian and Kun, namely, a circle from the Posterior Heaven to the Anterior Heaven, or a “return” in another term. Since the “return” in this case pointed to a reversion to the original state, the character “small” was used. Liu Yingming, a famous Daoist scholar in the Qing dynasty, likened it to “resuming all stuffs of the old home, and reclaiming its original simplicity.” He suggested that the Return to Original Simplicity constituted the most important aspect of cultivation. Without it, other refinement and cultivation were out of question. In this sense, the Small Reversion Elixir constitutes the fundamental element in a bid to extend human life.