《徐霞客游记·粤西游日记三十三》
堡南距洋渡仅三里。洞口向东，洞中深五六丈，后面洼下去，不能深入。
其门东向，中深五六丈，后洼而下，不能深入。
Baonan is only three li from Yangdu. The cave entrance faces the east. The cave itself is five or six zhang deep and dips down on the far side. It is impossible to enter any further.