An Older Map That the Later Schools Redrew

The fourfold classification familiar from the Sakya, Kagyu and Gelug curricula, kriya, charya, yoga and the single broad category of anuttarayoga or highest yoga tantra, is a product of Tibet's so called later translation period beginning in the eleventh century, built around texts brought from India during that second wave. Nyingma's ninefold scheme is older, tied to the earlier translation period associated with Padmasambhava and the imperial court, and it keeps the highest tier split into three rather than folded into one, mahayoga, anuyoga and atiyoga each treated as a distinct vehicle with its own texts and approach rather than as subdivisions of a single anuttarayoga class. That difference became a live controversy once the new schools were established: some later scholars questioned whether every text Nyingma classed as an authentic Indian tantra from the early period actually had an Indian original behind it, a doubt Nyingma scholars such as Rongzompa answered at length in the text's own defense. The nine vehicle scheme is therefore not simply a different way of counting the same material; it marks out a body of scripture whose Indian pedigree the newer schools were, at various points, prepared to dispute.