《徐霞客游记·楚游日记十四》
又往西有一条石缝，我侧身走进去，随后折往南面朝下走，穿过孔穴甸甸着身体爬出岩前，这是个透亮的小孔 我又从屋内进到洞中休息了一小会，仍旧回到前宫辞别了乘宗，从宫内右边攀登山岭，冒雨往北朝上走一里，就是中观。
又西有一隙，侧身而进，已转南下，穿穴匍伏出岩前，则明窦也。复从楹内进洞少憩，仍至前宫别乘宗，由宫内右登岭，冒雨北上一里，即为中观。
Further west, there is a stone crack. I walked in sideways, then turned south and went downward, crawling out of the rock cave through a tight hole, which is a small hole that let's in light. I entered the cave again from the house to rest a bit, and then returned to the front palace to bid farewell to Chengzong. I climbed the mountain ridge from right side of the palace, and walked north for a mile in the rain, and arrived at Zhongguan.