Steady and comfortable

Yoga Sutras II.46
स्थिरसुखम्‌ आसनम्‌ - Sthira-sukham asanam

Asanas should be steady and comfortable. The third limb of Raja yoga is the asanas or postures. This is a whole subdivision of Raja yoga known as Hatha yoga, which works directly with the prana and kundalini, the more subtle energy currents in the body. Hatha yoga postures, always done in a specific order, massage the endocrine glands and release energy blockages in the system so that a meditative stat is brought about physically rather than through sitting and watching the mind. Hath yoga is best practices in conjunction with meditation for the asanas are a vital aid, but not the end, on the path of samadhi.