During the Jin Dynasty, a hospitable man named Yue Guang, who lived in Henan, noticed that a friend had not visited him for a considerable time. Feeling puzzled, he decided to visit his friend.

The friend explained that during his previous visit to Yue Guang's home, he had seen what looked like a small snake in his wine cup. After unknowingly drinking it, he became severely ill upon returning home.

Baffled, Yue Guang returned to his own house to investigate. He soon discovered the truth: a horn-shaped bow was hanging on the wall, and its shadow was cast into the wine cup, making it appear like a snake.

When the friend heard this explanation, his illness instantly vanished.