《徐霞客游记·粤西游日记十二》
向导介绍着它，却不知我已游览过它；我从前游览它时，却不知洞叫什么名字。
导者言之，而不知余之已游；余昔游之，而不知洞之何名。
The guide introduced it, but did not know that I had already visited it; when I visited it before, I did not know what the name of the cave was.