Yogācārabhūmi Śāstra, Volume 34 (25)

Original text: 如是且由现见增上作意力故。十五种行观察内事。种种变异无常之性。观察是已。复更观察十六外事。种种变异无常之性。云何观察地事变异无常之性。谓由观见此地方所。先未造立道场。天寺宅舍。市廛城墙等事。后见新造善作善饰。复于余时。见彼朽故圮坼。零落颓毁穿缺。火所焚烧。水所漂荡。见是事已。便作是念。如是诸行。其性无常。何以故。如是色相前后转变。现可得故。

Explanation: Thus, by the power of intensified attention (adhimātra-manaskāra-bala) arising from direct perception, one observes the various marks of impermanence and transformation of the fifteen kinds of internal matters; after this observation, one then continues to observe the various marks of impermanence and transformation of the sixteen kinds of external matters. How does one observe the impermanence and transformation of land affairs (bhūmi-vastu)? One observes the location of this land, where previously no practice halls, temples, dwellings, marketplaces, city walls, and so forth had been built; later one sees these structures newly built, well constructed and well adorned. Then at another time, one sees those structures decayed and crumbling, fallen into ruin and collapse, worn away and breached, burned by fire, or swept away by water. After observing these things, one then has this thought: such conditioned formations are truly impermanent in nature. Why is this said? Because the transformation of their material forms from before to after can be directly observed in the present.