All four of these yoga practices are very different that what most westerners today would consider yoga. Very little - if any - of the focus was on the postures/poses (asanas). If fact, only the Raja Yoga as described by Patanaji even mentions asana or posture - and even then - he only mentions it three times (2:46, 2:47 & 2:48).
So if all this ancient talk about yoga had very little if anything to do with asana or posture, what was it about? And when they talked of PRACTICING yoga - what were they practicing if not postures?
Verse 1:12 of Patajali's Yoga Sutras gives us a hint -
Abhayasa Vairagyabhyam taniroddah - meaning: Constant Practice (Abhyasa) of Detachment (Vairagyabhyam) is the method to still the movements of the mind (tanirrodah).
The practice of yoga was to "redirect" the mind - to "still the movements" of the mind - to "focus" the mind. And, the practice was to do this through either detachment, service, devotion or Patanjali's eight-limbs or "ashtanga" yoga, which included deep meditation.
Therefore, for today's practitioners - in addition to practicing sirsasana (headstand), practice compassion. In addition to practicing sarvangasana (shoulderstand) practice detachment from the result of the pose. In addition to practicing uttanasana (standing forward fold) practice looking inward at your true self.
This is the practice - the practice of quieting, redirecting, focusing the mind to be a servant and not a master.
I heard a great phrase which captures this inward journey to the anandamaya kosha (the innermost sheath of our true nature). The statement was this:
"Now that I know who I am, I don't have to be who I was."