About a definition of asana, yoga pose, we can quote Patanjali, which enunciates in three brief aphorisms the principles on which the asanas, their objectives and effects, are established, as well as the process through which such effects are achieved. It is appropriate to underline that all of this concerns the static aspect of the asana.
“The posture must be stable and pleasant.”
This aphorism gives us an idea of the principal characteristics of an asana: it tells us in fact that it contributes to the “stability” and it gives a sense of comfort.
The term “stability”, in this case, doesn’t mean only stability of the position, but it refers to the stability of the body and mind intended as a whole. In fact, even if the yogi is “stable” on the physical plan, it is possible that he is unstable on the mental plane because of some disturbing factor.
But when the physical stability is joined to the mental, then it is reached a state of comfort. Nevertheless the aphorism doesn’t mean that every easy position to be achieved and able to be maintained in a stable way is an asana: if that was so the state of sleep would be the best of the asanas, because it is an easy position to maintain.
But naturally, since the term asana recalls a sitting position and implicates a state of awareness, the asana cannot be a state of sleep: the asana can be defined instead as a postural model that conducts to the physical and mental stability and to a condition of comfort.