For most of its history yoga passed directly from teacher to student, with written texts playing a supporting role rather than a primary one. The surviving literature was shaped by that arrangement, and reads oddly when the arrangement is forgotten.
Instruction was personal and corrective
A teacher watching a student can see what a text cannot describe: where the breath catches, where the spine collapses, where effort has become strain.
Much of the instruction was therefore adjustment rather than exposition, delivered in response to a particular body on a particular day.
Almost nothing of that kind survives in manuscripts, since corrections were spoken and specific to one occasion. Reconstructing historical practice from texts alone therefore leaves gaps that no amount of careful reading can close.
Memorisation preceded understanding
Students commonly learned verses by heart before being taught their meaning, a pattern found across Indian scholastic traditions.
The sequence is efficient under oral conditions. The text is secured first, and explanation can then be supplied gradually over years of contact.
It also meant the wording remained stable while interpretation varied, which is why lineages sharing identical verses can teach noticeably different things.
Lineage functioned as authority
Legitimacy came from the chain of teachers a practitioner could name rather than from a book they had read or a certificate they held. Knowing who taught whom was the standard way of assessing a claim.
Texts often open by placing themselves in such a chain, which is a claim about transmission rather than about authorship in the modern sense.
Where the chain is intact, a lineage can explain what its verses mean; where it broke, later readers face a text without its instructions.
Terseness was a feature of the system
Written works could stay short because they were never expected to carry the whole teaching. They indexed material held in memory and delivered in person.
Manuals accordingly name practices without describing them fully, and describe practices without naming the conditions under which a teacher would consider giving them to a particular student.
Reading them as complete manuals produces a misleadingly thin picture of what practitioners actually did. The written record is an index to a practice, not a transcript of one.
What printing and travel changed
Once texts circulated widely, students could encounter practices without a teacher, and the balance between book and lineage shifted decisively.
Photography and later film extended this, allowing postural detail to be transmitted visually in a way manuscripts never could.
The gain in reach came with a loss in correction, and much modern teacher training is an attempt to rebuild the supervisory layer that transmission once supplied by default.