《徐霞客游记·黔游日记四》
外层就是洞口以内靠前面的部分，空阔得有如宽敞的殿堂，中央有块圆石，如人工用刀子削圆的一样。
外层即洞门之前，旷若堂皇，中有圆石，如堆旋而成者。
The outer layer is the part just inside the entrance, which is as spacious as a spacious hall, with a round stone in the center, as if cut into a round with a knife.