Within the Great Perfection, the textual foundation is traditionally understood through the threefold division of Semdé (Mind Series), Longdé (Space Series), and Menngagdé (Instruction or Upadeśa Series). The Mind Series represents some of the earliest Dzogchen literature and emphasizes direct recognition of mind-as-such; here, the *Kunjed Gyalpo* (Kun byed rgyal po, “All-Creating King Tantra”) is regarded as a root scripture, accompanied by related Semdé tantras and explanatory works. The Space Series focuses on the vast, open dimension of reality (klong), with its own set of “Space Tantras,” some of which are counted among the most revered Dzogchen scriptures. The Instruction Series is held to be the most direct in terms of pith guidance for realization, and it is in this class that the tradition locates its most refined expositions of view and practice.

At the heart of the Instruction Series stand the Seventeen Atiyoga Upadeśa Tantras, regarded as the core tantras of Dzogchen in the Nyingma school. These “Seventeen Tantras” are treated as encapsulating the essential view and method of the Great Perfection, and many later systems look back to them as their root. They include key works that are closely linked with the later Heart Essence (sNying thig) transmissions, which draw on these tantras for both doctrinal grounding and meditative instruction. When practitioners and scholars speak of the central Dzogchen tantras, it is often this group of Seventeen Upadeśa Tantras that is being invoked.

From the perspective of lived practice, the Heart Essence (sNying thig) cycles become almost as foundational as the earlier tantras themselves. Cycles such as the Vidyādhara Heart Essence, Vimalamitra’s Heart Essence, the Khandro Nyingthig, and the Longchen Nyingthig are revered as concentrated streams of pith instruction. Although technically later developments, they are rooted in the Seventeen Tantras and related Atiyoga scriptures, and thus serve as a bridge between the primordial tantras and the concrete contemplative life of practitioners. In this way, the tradition holds together a canon that is both ancient and ever-renewed, with the Heart Essence cycles continually rearticulating the original tantric vision.

All of these materials are preserved and contextualized within the broader Nyingma tantric corpus. The Nyingma Gyubum (rNying ma rgyud ’bum), the collected Nyingma tantras, houses the principal Dzogchen tantras, including the Seventeen Tantras and many of the Mind, Space, and Instruction Series scriptures. Some Atiyoga and Dzogchen works also appear in the general canonical collections of Kanjur and Tanjur, yet the living heart of the Great Perfection tantras is maintained above all in the Nyingma Gyubum. Taken together, these scriptural strata form a layered but coherent foundation for the tradition’s direct approach to recognizing the nature of awareness.