In the Yoga Sutras, Patanjali defines asana as to be seated in a position that is firm, but relaxed. Patanjali mentions the ability to sit for extended periods as one of the eight limbs of his system, known as ashtanga yoga, but does not mention standing postures.ranayama, or breath control, is the Fourth Limb of ashtanga, as set out by Patanjali in the Yoga Sutra. The practice is an integral part of both Hatha Yoga and Ashtanga Vinyasa Yoga in the execution of asanas.