《徐霞客游记·浙游日记下》
走出内洞，左边又有两个洞，下洞延伸进去不多远，上洞也如夹室一样曲折，右边有一个悬空的孔穴，从孔穴中向下窥视幽深无底，我猜想那里就是内洞坠陷的最深处。
既出内洞，其左复有两洞，下洞所入无几，上洞宛转亦如夹室，右有悬窍，下窥无底，想即内洞之深坠处也。
I went out of the inner chamber and saw two more caves on the left. The lower of these did not lead very far, but the upper one was tortuous like a narrow chamber, and there was a hole in the roof on the right from which I could look down into an unfathomable abyss. I guessed that this was the lowest point of the collapse in the inner cave.