The story is recorded in Huai Nan Zi.
    "Once upon a time, Yi, the hero who had shot down nine suns, went to Xi Wang Mu, the Mother Goddess for the elixir. It was said that anyone who ate the elixir could rise to the moon and become the god of the moon. Knowing this, Chang E, Yi' s wife stole this magic medicine and rose onto the moon and became the goddess there. Yi felt terribly disappointed for los-ing both his wife and the elixir, because both of them were unique."