I Ching
Interpreted by wu wei

The Principle

Using the yarrow stalks, the person asking the question grasps a portion of stalks from a bunch of forty-nine stalks. The person cannot know how many stalks he is grasping, and, therefore, exceeds the capacity of his rational mind; thereby, he enters into the purely spiritual world where some part of him knows exactly how many stalks he has grasped. With the coins, the person asking the question shakes three coins in his cupped hands and throws them onto a flat surface. The person cannot know how they will land and so exceeds the capacity of his rational mind to control the outcome. In that regard, the two methods utilize the same principle.
The reasons for the inaccuracy in the coin method are that the statistical results of the coin method are different from those of the yarrow stalk method, and, as a result, the coin method usually produces too many moving lines, which results in obtaining an incorrect second kua and incorrect information in the first kua. Because the coin method is quick and easy, it is highly popular. It is worthwhile to take the time to understand why the results are different so that you will refrain from its use.