Yogācārabhūmi-śāstra: Volume 34 (Part 14)

How to contemplate the nature of impermanence manifested through the transformations of form in internal matter? It is stated that just as with perceptible colors, so too should one understand the same principle regarding bodily form in terms of plumpness and thinness. How to contemplate the nature of impermanence manifested through the transformations of rise and fall in internal matter? By observing either oneself or others, one may first see that relatives, wealth, and status are all in a state of prosperity; later, one may see that everything has declined; yet again at a later time, one may see prosperity return. Having witnessed such phenomena, one thinks to oneself: "All such conditioned things are indeed impermanent in nature. Why? Because the transformations of rise and decline are presently observable."