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 nature of mountain affairs (parvata-vastu) as impermanent and subject to change? At one time, one sees a mountain range with lush, dense forests and towering rocks and precipitous cliffs reaching into the clouds; at a later time, one sees those forested mountains and towering rocks withered, ruined, and crumbling, about to collapse, jagged and uneven—either burned by fire or washed away by water. After observing these things, one thinks in one's mind: such conditioned formations are truly impermanent in their nature.