《徐霞客游记·游黄山日记》
大约平天斑的南面是前海，北面是后海，就是最高的地方，四面都是险峻的凹地，唯独这里有如平地。
盖平天矼阳为前海，阴为后海，乃极高处，四面皆峻坞，此独若平地。
It is estimated that the south of Pingtianban is the front sea, and the north is the back sea. This is the highest place, where there are dangerous concave places on all sides, but this place is like a flat land.