So the student first works around Bhujaṅgāsana
within their personal practice and the information that arises
guides the teacher as to their readiness for, in this case, Sarvāṅgāsana.
The information arising from observing how
the student practices Bhujaṅgāsana guides
the teacher as to the appropriateness of Sarvāṅgāsana.
The information that feeds back may be on the level
of Annamaya, Prāṇamaya, Manomaya or beyond.
Obviously, this implies that we are observing the student’s practice directly.
Once the student shows an adequate performance of Bhujaṅgāsana
and it can be integrated into their existing personal practice,
then we can be more secure that the student is ready to approach
integrating Sarvāṅgāsana into their regular practice.