Steadiness and ease in asana
Patanjali describes asana in terms of steadiness and ease. Iyengar develops that brief definition into a discussion of what happens in the body and attention while we hold a posture.
What steadiness feels like
A position can look still while requiring considerable effort. A person might clench the jaw, lift the shoulders, or shift weight to keep the shape. Iyengar pays attention to how the parts of the body work together. Consider both the stability of your support and how much effort it takes to maintain it.
Where attention goes
When attention is absorbed by one movement, we can overlook tension nearby. In a familiar position, notice the support, face, and shoulders in turn. Then notice the position as a whole. This illustrates the idea of distributing attention while leaving the choice of posture to you.
A simple observation
Sit in an ordinary position with comfortable support. Notice where your body meets the seat, where your feet rest, and whether your breath is moving freely. Change position if you become uncomfortable. Stop if you feel pain, numbness, or dizziness. A brief observation is enough to notice some of the conditions that make the position feel steady.
How support changes the work
In an ordinary seated position, you may feel more weight on one side of the seat or one foot. That observation gives you information before you make any adjustment. If the feet barely reach the floor, for example, you could choose a seat that lets them rest more easily. Notice what happens to the shoulders or jaw when the support changes. Iyengar’s interest in the relationship between the parts of the body makes this kind of comparison more informative than judging the outline of the posture alone.
Easing effort while keeping the shape
The sutra after the definition of asana links posture with the easing of effort. A useful way to understand this is to distinguish the work of remaining supported from tension that gathers elsewhere. The torso may still need to organize itself while the fingers can rest loosely. Both are happening in the same position. When the hands relax, notice whether you can remain as steady as before. That gives you something specific to observe about effort and ease.
Comparing two moments in one position
Give yourself enough time to notice how a position feels at the beginning and a little later. At first, attention may be drawn to finding your seat or placing your feet. Once you have settled, another area of the body may become more noticeable. Iyengar’s account makes room for this change in awareness. A comparison of two moments can tell you more about the posture than a photograph of either moment on its own.
Reading the sutras
Sutras II.46–II.48 associate steadiness with the easing of effort. In Iyengar’s reading, the way body and attention work together tells you something about the quality of a posture.
Source
B. K. S. Iyengar. Heart of the Yoga Sutras.