Yoga Sūtra Chapter Two verse 46
Steady and comfortable is posture.sthira - steadysukha - happiness; comfortable; pleasantnessāsana - posture
Commentaries and ReflectionsTKV Desikachar:
“Sthira Sukham should both be present in Āsana.
It also implies one should be able to choose the breath ratio.
If we are doing Āsana and the mind continues to wander,
we are not doing the Āsana, only our bodies are doing them.”
“To experience Āsana is
to meld the Mastery of outer Stillness to the world
into the Mystery of inner Openness to the beyond.”