The figures of the Toad and the Rabbit in the Moon most likely came from the appearance to the ancients of lunar shadows. Ancient myths already mention a jade rabbit that grinds the elixir of immortality beside the Queen Mother of the West, but the story of the lunar cassia tree endlessly chopped by Wu Kang is a later creation.
蟾蜍、月兔的形象大抵由古人觀察月亮的陰影所得；古代神話中的西王母身旁已有搗藥（不死之藥）的玉兔；至於吳剛伐桂則又是後來產生的故事。