Introduction to Dongtian Yipin: When Mi Fu was 42 years old, he built a house by the Linshi River "to the west of Dan Tuxing Yamen" and named it "Xishan Academy". Mi Fu's calligraphy in "Hai Ju Tie" recorded the bamboos, trees, water, stones, halls, halls, pavilions and pavilions of Xishan Academy. Among them are detailed descriptions of "a first-grade stone in the cave sky" and "eighty-one holes, as big as a bowl and as small as a finger". The stone is full of nectar and is as white as jade. The meaning and scenery are what everyone sees as "the first level of the cave sky", which means that you can walk through it comfortably, and when you pass through it, you will reach the first level.