Yogācārabhūmi-śāstra: Volume 34 (Part 18)

How to contemplate the cold and heat of internal matters, the nature of change and impermanence that arises? It is said that by observing oneself or others at the time of extreme cold, the body is uncomfortable, curling up and shivering, cold freezing and pressing, hoping to encounter warm sunlight. At the time of extreme heat, the body is comfortable, stretching and dry-mouthed, sweating like drizzle, heat and thirst pressing, hoping to encounter coolness. Again when it becomes cold, seeing the appearances as previously described. Having seen this, then thinks thus: Thus all conditioned phenomena are impermanent in nature. The rest as previously said.

How to observe the nature of change and impermanence that arises due to cold and heat in internal bodily matters? By observing oneself or others at the time of extreme cold, the body is very uncomfortable, curling up the body and shivering all over, cold pressing the body, hoping to obtain warm sunlight. Or observing at the time of extreme heat, the body stretches out, the whole body is hot and dry, mouth dry and tongue parched, sweating all over like rain, both hot and thirsty, hoping to encounter coolness. Afterwards when it becomes cold season, again seeing the phenomena and states as mentioned before. Observing these phenomena, then has this thought in mind: Thus all conditioned phenomena are truly impermanent in nature.