Yogācārabhūmi-śāstra: Volume 34 (33)

How is it that one observes the impermanent nature of the changing light? It is said that by perceiving the arising and ceasing of various states of brightness and darkness, along with their transformations, and having observed this, one forms the thought: "Such conditioned phenomena are indeed impermanent by nature." The rest is as previously explained. How is it that one observes the impermanent nature of the changing affections between men and women? It is said that one observes them either declining or flourishing, not enduring steadfastly for long. Having observed this, one forms the thought: "Such conditioned phenomena are indeed impermanent by nature." The rest is as previously explained.