The Yi Jing (also spelled I Ching) or "Book of Changes" is a classical Chinese text based upon 64 hexagrams, each of which is represented visually as a series of six broken or unbroken lines, stacked vertically. The 64 hexagrams are based upon the bagua, and represent stages in a continuing process of change.
In the west, the Yi Jing is known primarily as a tool for divination. Traditionally, yarrow sticks are cast upon the ground, with the resulting pattern corresponding to a particular hexagram. The Yi Jing can be consulted also by using three pennies. The Taoist I Ching, translated by Thomas Cleary, which includes commentary by the Taoist adept Liu I-ming, is particularly relevant for Taoist practitioners.