《徐霞客游记·游雁宕山日记》
洞门东向，洞门口有一石桥，从洞顶斜插于地上，有如飞虹下垂。
洞门东向，门口一梁，自顶斜插于地，如飞虹下垂。
The entrance of the cave faces east, and there is a stone bridge at the entrance of the cave, which is inserted into the ground from the top of the cave, like a flying rainbow hanging down.