Yogācārabhūmi-śāstra, Volume 34 (27)

Original text:云何观察山事变异无常之性。谓于一时观见其山。丛林蓊郁。耸石巉岩。复于一时见彼丛林。巉岩耸石。雕残颓毁。高下参差。火所焚烧。水所漂荡。见是事已。便作是念。如是诸行。其性无常。余如前说。

Explanation: How does one observe the mountain phenomena—the nature of change and impermanence in mountains and ranges? At one time, one sees a mountain range with lush, dense forests and towering crags and precipitous rocks rising into the clouds; at a later time, one sees that same forested mountain with its crags and towering rocks withered, broken, and crumbling, tottering as if about to collapse, jagged and uneven—either burned by fire or washed down by water. Having observed these things, one then thinks in the mind: such formations as these are truly impermanent in their nature.