According to Nyingma accounts, when Padmasambhava travelled through Tibet and the Himalayas in the 8th century establishing Buddhism, he did not force the teaching on places or people not ready for it. Instead, in locations he judged unprepared, he concealed the necessary instructions as terma — treasures, sometimes physical texts and objects hidden in caves, cliffs, rivers and statues, sometimes said to be planted directly in the mind-stream of a disciple who would be reborn centuries later as a tertön, a "treasure revealer," to bring the teaching forward at the right moment.
The location of each beyul was itself recorded as a kind of terma: guide scrolls called lamyig or neyig, hidden under rocks and inside monasteries and stupas, to be found only when a qualified tertön was moved by vision to seek them out — meaning access to a beyul has historically required not navigation skill but spiritual authorization, arriving on the tradition's own timetable rather than the seeker's.