Yoga Rahasya Chapter One verse 31

sthūlaḥ kṛśas-tathā śuṣkaḥ vakraḥ paṅguḥ śarīrataḥ |
atas-teṣāṃ na sarvāṇi vihita-anya-āsanāni vai ‖

There are different body structures,
therefore not all Āsana are enjoined.

sthūla - gross, tangible, material; large, thick, stout, massive, bulky, big, hugekṛśa - lean, emaciated, thin, spare, weak, feebletathā - so, like, after that manner.śuṣka - dried, dried up, dry, arid, parched, shrivelled, emaciated, shrunk, witheredvakra - crooked, curved, bent, tortuous, twisted, wry, obliquepaṅgu - of those elements of the body which are themselves without motion; lame, halt, crippled in the legsśarīra - the body, bodily frame, solid parts of the bodyataḥ - therefore, thus, consequently, henceteṣām - of those, amongst them; all of themna - no; not; nor, neithersarva - whole, entire, all, every one; altogether, wholly, completely, in all parts, everywherevihita - destined or meant for; prescribed, decreed, enjoinedanya - the other; other than, different from, opposed to; other, differentāsana - particular posture; sitting, sitting down; seat, place, stool; abiding, dwellingvai - a particle of emphasis and affirmation, generally placed after a word and laying stress on it

Commentaries and Reflections

Commentary by T Krishnamacharya:

“There are different body structures,
therefore not all Āsana are enjoined.”