Yogācārabhūmi-śāstra, Volume 34 (18)

Original text: 云何寻思内事寒热。所作变异无常之性。谓由观见。或自或他于正寒时。身不舒泰。踡局战栗。寒冻缠逼。希遇温阳。于正热时身体舒泰。奋身干语。霡霂流汗。热渴缠逼。希遇清凉。复至寒时。还见如前所说相状。见是事已。便作是念。如是诸行。其性无常。余如前说。

Explanation: How does one contemplate the impermanent nature of the changes brought about by cold and heat in the internal phenomena of one's own body? By observing that oneself or others, when experiencing extreme cold, feel bodily discomfort—curling up and trembling all over, beset and pressed by the freezing cold, longing to encounter warm sunlight. Or one observes that when experiencing extreme heat, the body stretches out and relaxes, the whole body feverish and parched, with sweat pouring down like rain, hot and thirsty, longing to encounter coolness. Later, when the cold season comes again, one sees the same phenomena and states as described before. Having observed these phenomena, the following notion arises in the mind: such formations are truly impermanent in their nature.