
You might also find this previous comment of mine useful - https://news.ycombinator.com/item?id=41538322
In Patanjali Yoga Sutras the concept of "God" is merely used as an entity and technique to help you in your practice to break out of your self-identity (i.e. Ahamkara). It is just one among a set of techniques. There is only half a dozen sutras which even mention god in the entire text (see this succinct translation by Bon Giovanni - https://sacred-texts.com/hin/yogasutr.htm). It is in the later commentaries on the text that you find an elaboration according to the pre-existing beliefs of the author.
To see how succinct they are, read Bon Giovanni's translation at https://www.sacred-texts.com/hin/yogasutr.htm
If you are new to the subject start with Swami Vivekananda's Raja Yoga which is a very loose but accessible overview.
For a detailed study with notes from various commentaries, see The Yoga Sutras of Patanjali trans. by Edwin Bryant.
The above two should give you a solid foundation after which you can move on to even more exhaustive translations with specific commentaries.
Asana is only one specific part of the entire practice. It’s a good beginning point. But it’s also very clear from texts like Hatha Yoga Pradipika, Vasistha Samhita, Patanjali Yoga Sutras, Vajrayana Buddhist yoga texts, and others that yoga definitely isn’t a Scandinavian invention.
IMO, Sanskrit persisted as the language of metaphysical and scientific treatises for a long time because of practical advantages. A large library of concepts, allowed easy reuse and concision [1]. Being trained in Vedanga (phonetics, metre, grammar, etymology, etc.) allowed practitioners to compose new sutras easily, much like PhD students using mathematical notations and proofs in papers.
It was used conversationally, at least in courts and debates. Its decline into a quasi-venerated read-only language over the last 1000 years would be an interesting (and contentious) topic for dissertation.
[1] Patanjali Yoga Sutras http://www.arlingtoncenter.org/Sanskrit-English.pdf
