Yogācārabhūmi-śāstra, Volume 34 (Section 28)

Original text: 云何观察水事变异无常之性。谓先一时见诸河渎。池泉井等。涛波涌溢。醴水盈满。后于一时。见彼一切枯涸干竭。见是事已。便作是念。如是诸行。其性无常。余如前说。云何观察业事变异无常之性。谓先一时。见彼种种殉利牧农。工巧正论。行船等业。皆悉兴盛。复于一时。见彼事业皆悉衰损。见此事已。便作是念。如是诸行。其性无常。余如前说。

Explanation: How does one observe the impermanent nature of the changes in water matters (udaka-vastu)? At an earlier time, one sees rivers, streams, ponds, springs, wells, and the like, with surging waves overflowing and sweet water filling them full; at a later time, one sees all those rivers, springs, and ponds completely dried up and exhausted. After observing these phenomena, one then thinks in this way: such conditioned formations are truly impermanent in nature. How does one observe the impermanent nature of the changes in occupational matters (karma-vastu)? At an earlier time, one sees that various undertakings pursued for worldly gain—herding and farming, crafts and skills, proper discourse and debate, ship transport, and the like—are all flourishing; then at a later time, one sees that all these enterprises have declined and deteriorated. After observing these phenomena, one has this thought in mind: such conditioned formations are truly impermanent in nature.