I Ching
Interpreted by wu wei

Methods of Inquiry

Two methods of asking questions were devised by the ancient sages: the tortoise shell method and the yarrow stalk method. (The answers to the questions were usually carved on bones.) The tortoise shell method, which entailed heating a tortoise shell until it cracked, is lost to us, but the yarrow stalk method is available and will be explained later in detail.
Many people today use a coin method, which is quick and easy, but my experience and that of others have revealed that the answers obtained using the coin method are somewhat inaccurate and, therefore, unreliable. The coin method may seem to produce accurate results, but that is because the same principle (explained below) is used to obtain the kua.