I Ching (Yi Jing 易经) is the very foundation of Daoism and Chinese culture. But I Ching that we normally refer to is just one-third of all I Ching that was created by the ancient Chinese.
This one-third of I Ching we know today is actually called “Zhou Yi (Change in Heaven 周易)”, meaning: “the I Ching compiled during the Zhou Dynasty” (1100 BC – 221 BC). It consists of three key parts: concepts (li 理), charts (xiang 象) and numbers (shu 数), and illustrates three fundamental tenets: transcendence of all things (bianyi 变易), simplicity of underlying principles (jianyi 简易) and eternality of unblemished Dao (buyi 不易).
The other two I Chings are Lianshan (Link to Mountain 连山) and Guicang (Save in Earth 归藏), both were evidently compiled before that of Zhou Yi.
Unlike Zhou Yi that starts with the hexagram of Heaven, in Lianshan the first hexagram is Mountain, and in Guicang it is the Earth hexagram that tops the rank.
While Zhou Yi is believed to be compiled by Duke Zhou and Lianshan is allegedly created by Red Emperor – who was a thousand-year older than Zhou – Guicang is said to have an even more venerable author: the Yellow Emperor himself.
There are purported original texts of Lianshan and Guicang in Books Discovered in Three Ancient Tombs (Gusanfen Shu 古三坟书) and Lost Classics Recovered by Yuhanshan Studio (Yuhanshanfang Yishu 玉函山房辑佚书), but both are considered fake by most experts.
In March 1993, a large number of fragmented bamboo books were unearthed from a tomb dating back to the Qin Dynasty (221 BC – 207 BC). It contains over 4000 characters and more than 70 charts on the topic of Guicang. However, a readable version of any page is yet to be reconstructed.
Three I Chings, apparently, contemplate the universe from slightly different angles. Zhou Yi places its emphasis on Heaven, Guicang views the world from the perspective of Earth, while Lianshan focuses on Mountain, the linkage between Heaven and Earth.