A modern class is built on standing postures. Warriors, triangles, lunges, standing forward bends and the sequences that link them make up most of the time on the mat in the styles that spread worldwide in the twentieth century. The classical manuals contain almost none of it.
Counting the two surviving hatha texts together, the postures performed on the feet can be listed in a sentence: the tree, the raised posture, the winding of sankatasana. Everything else sits, kneels, lies prone or balances on the arms. That imbalance is the single largest difference between the medieval literature and contemporary practice, and it is much larger than any difference in how an individual posture is performed.
Mark Singleton's Yoga Body documents where the standing repertoire came from, tracing the formation of modern posture practice in early twentieth century India out of the hatha inheritance together with indigenous physical culture, wrestling and gymnastic traditions and the European physical culture movement that was circulating at the time. The account is documentary rather than deflationary: it does not argue that modern practice is fraudulent, only that it has a history, and that the history is recent for a large part of what is now taught. The atlas records sankatasana as one of the very small number of standing forms the classical corpus actually attests.