There was once a painter in the Southern and Northern Dynasties Period named Zhang Sengyou. One day, he visited a temple and painted four dragons on the walls, but gave none of them eyes. The other visitors to the temple found this strange, and asked him why he hadn't painted the eyes. Zhang Sengyou told them that the eyes were the most important part of a dragon, and with their eyes, the dragons would fly away. Nobody believed this, and so to prove his point, Zhang Sengyou added eyes to two of the dragons. No sooner had he painted the last eye did a crack of thunder sound and the dragons fly off. The two without eyes remainded on the wall.