《徐霞客游记·粤西游日记七》
此道裂隙开始进去时十分狭窄，稍微进去后往西走，便上下都似苍弯一样，黑暗得不能辨认东西。
其隙始入甚隘，少进而西，则高下穹然，暗不可辨。
This road began to go in very narrow, After going in a little bit and walking to the west, it looked like a dark bend both up and down, and nothing could be recognized.