In the dark sea of the north there is a fish; it is named the Kun. The Kun is so huge no one knows how many thousand li he measures. Changing, it becomes a bird; it is named the Peng, so huge no one knows how many thousand li he measures. Aroused, it soars aloft, its wings like clouds hung from the sky. As the sea shifts, it turns to set its course toward the dark sea of the south, the Pool of Heaven.
—The Peng Bird, Free and Easy Wandering, Chapter 1, The Zhuanghzi (the Daoist text) written by Zhuanghzi