“Sthira Sukha (Yoga Sūtra Chapter Two verse 46) should both be present in Āsana.
It also implies one should be able to choose the breath ratio.”
– TKV Desikachar England 1980

Yoga Sūtra Chapter Two verse 46 Sthira Sukham Āsanam
“Means what happens before and after a posture.
One should be able to move to another posture with ease.
– TKV Desikachar England 1980

“Sthira is the absence of Rajas.”
– TKV Desikachar commentary on Yoga Sūtra Chapter Two verse 46

“The experience known as Sthira Sukham Āsanam,
described in Yoga Sūtra Chapter Two verse 46,
arises as a fruit of Yoga Sūtra Chapter Two verse 47,
from melding the mastery of outer stillness in the world,
described as Prayatna Śaithilya, or relaxation of continued effort,
with the mystery of inner openness to the beyond,
described as Ananta Samāpatti, or unity in the infinite.”
– Reflections on Yoga Sūtra Chapter Two verse 46

“Without Āsana,
Prāṇāyāma cannot become accomplished.
Without containing Prāna,
the mind cannot achieve steadiness.”
– From T Krishnamacharya’s composition,
The Yoga Rahasya Chapter One verse 45

Links to Related Posts:

The Viniyoga of Āsana Part 1 of 15 – Āsana according to Haṭha and Rāja

Question to Krishnamacharya – “Can you explain the concept of Vinyāsa and Pratikriyā Āsana?”