2.46 sthi rasukh amā sanaman

Asanas must have the dual qualities of alertness and relaxation. Steady and comfortable.

2.47 prayat naśait hilyānantas amāpattibhyām

Alertness and relaxation can be achieved by recognizing and observing the reactions of the body and breath to the various postures that comprise asana practice.

2.48 Tato dvaṅdvā nabhi ghātah

When these principals are correctly followed, asana will help a person endure and minimize external influences on the body such as age, climate, diet and work.