The first of the seven bitter mountains in the middle is called Xiu Yushan. There is a stone on it, which is called the chess piece of the Emperor's Platform. It has five colors and text, and its shape is like a goose egg. It is the stone of the Emperor's Platform. Therefore, those who pray to the hundreds of gods will not be poisoned by it.
——"The Classic of Mountains and Seas. Zhongshan Classic"