Yogācārabhūmi Śāstra, Volume 34 (23)

Original text: 云何观察内事终殁。所作变异。无常之性。谓由观见。今时存活。安住支持。复于余时。观见死没。唯有尸骸。空无心识。见是事已。便作是念。如是诸行。其性无常。云何观察内事青瘀等。所作变异。无常之性。谓由观见。死已尸骸。或于一时至青瘀位。或于一时至脓烂位。如是乃至。骨锁之位。见是事已。便作是念。如是诸行。其性无常。

Explanation: How does one observe the impermanent nature of the changes that occur in internal matters (bhūmi-vastu) at the time of death? One observes that another person is still alive at present, dwelling securely in the world, and later discovers that he has died, leaving behind only a corpse, devoid of mind and consciousness. After observing this phenomenon, the mind gives rise to such a thought: such volitional formations are truly impermanent in nature. How does one observe the impermanent nature of the changes that occur in internal matters at the stages of livid discoloration and so forth of the corpse? One observes the corpse of one who has already died: at one time it reaches the stage of livid discoloration and swelling, at another time the corpse shows the phenomenon of suppuration and festering, until in the end only a pile of bones remains. After observing these phenomena, the mind gives rise to such a thought: such volitional formations are truly impermanent in nature.