A Taoist formulation of divination, using sticks (usually Yarrow stalks). To determine the answer to a question, an appropriate time is chosen, and a ritual performed to create a specific number of lines. The process is repeated for each line of a trigram or hexagram. The resultant line formations are interpreted to determine the inevitable change of a Yin force into a Yang force and vice versa. These changes can ultimately produce any of 64 hexagrams, each of which can be interpreted using specific principles.
Books:
The I Ching, Book of Changes
I Ching: A New Interpretation For Modern Times, by Sam Reifler [ISBN 0-553-13677-1]