Some Advice on the Practice of Āsana from a Medieval Jain


Rishabhanatha seated in Two Stages of Meditation
Five Auspicious Events in the Life of the First Jina
Panchakalyanaka (ca. 1680)
Edwin Binney 3rd Collection, The San Diego Museum of Art

In the Jain text called the Jñānārṇava (circa 11th century), Śubhacandra gives advice on the practice of āsana:
On a wooden or stone slab, on the earth or sand, the wise [yogin] should adopt a very steady āsana for attaining Samādhi. 
Sages should perform that agreeable āsana by which they, sitting comfortably, can make the mind still. 
The rules concerning place and āsana are the foundation of success in meditation. 
Without either [the proper place or posture], the sage's mind will immediately be distracted. 
Now, the yogin whose senses have been subdued should master āsana
Those whose posture is very steady do not tire at all in Samādhi. However, because of a weakness in the practice of āsana, steadiness of the body is not experienced. Because of [such] a weakness in their body, [those people] certainly tire at the time of Samādhi. 
The yogin who has accomplished mastery of āsana does not tire even if afflicted repeatedly by wind, heat, cold, etc., and by [various] types of insects.
Translation by Jason Birch (2016).

Śubhacandra's Jñānārṇava

dārupaṭṭe śilāpaṭṭe bhūmau vā sikatāsthale |
samādhisiddhaye dhīro vidadhyāt susthirāsanam ||26.9||

yena yena sukhāsīnā vidadhyur aniścalaṃ manaḥ |
tat tad eva vidheyaṃ syān munibhir bandhurāsanam ||26.11||

sthānāsanavidhānāni dhyānasiddher nibandhanam |
naikaṃ muktvā muneḥ sākṣād vikṣeparahitaṃ manaḥ ||26.20||

athāsanajayaṃ yogī karotu vijitendriyaḥ |
manāg api na khidyante samādhau susthirāsanāḥ || 26.30||
āsanābhyāsavaikalyād vapuḥsthairyaṃ na vidyate |
khidyante tv aṅgavaikalyāt samādhisamaye dhruvam || 26.31||

vātātapatuṣārādyair jantujātair anekaśaḥ |
kṛtāsanajayo yogī khedito 'pi na khidyate ||26.32||