Zhuang Zhou, a representative Taoist figure in the Warring States Period, recorded in "Zhuangzi Xiaoyao Tour": It is said that there was a kind of Pengbird in ancient China, which was made by a big fish named Kun. Its back is thousands of miles long. Every June, it flies to the "Tianchi" in the South China Sea. As soon as it flapped its wings, the water in Tianchi was blown up by waves of three thousand miles. It can fly more than nine miles in a whirlwind.

Later, according to this story, people invented an idiom "Pengcheng Wan Li" to describe the boundless future.