Yogācārabhūmi-śāstra, Volume 34 (19)

How should one contemplate the inner affairs of dignified deportment and the nature of change and impermanence produced thereby? It is by observing oneself or others in walking, standing, sitting, or lying down, following one dignified deportment, sometimes causing harm, sometimes bringing benefit. Having seen this, one thinks thus: all such conditioned phenomena are impermanent in nature. The rest is as previously stated.

How to observe the nature of change and impermanence that appears in the inner bodily affairs regarding the four dignified deportments? By observing oneself or others when walking, standing, sitting, or lying down, following one dignified deportment, sometimes there is decrease, sometimes increase. After observing these phenomena, the thought arises in the mind: all such conditioned phenomena are truly impermanent in nature.