The most fundamental teachings which points the mind towards freedom, the authentic non-dual realization of the fundamental state, the primordial state, are the teachings of the Great-Perfection (Atiyoga). In the root text the Cuckoo of Pure Presence it says:
The nature of the infinite variety of phenomena is without duality,
since, each thing in itself (singularity) is beyond all concepts and limits of the mind.
The natural condition, suchness as-it-is, is beyond conceptual elaboration,
yet manifesting as all diversity of form - the radiance of Samantabhadra, all-good.
All is self-perfected in actuality, so the sickness of effort is liberated,
remain free and natural in the contemplation of spontaneous total presence.
The state of ground of reality, which is the same as the ground of being, is beyond all conceptual elaboration, the natural condition. The natural vibrant responsive, and dynamic, nature of the ground shimmers as timeless, infinite movements - when that is realized that is awakening, when it is not, then the entire universe appears. However, all the variety of appearances are in reality beyond duality and non-duality. Both the ideas of duality, that is the existence of truly existent subjects and objects, and non-duality as in the sense of oneness of everything, are not the true condition. They are both extremes which are not the primordial state. The true condition is non-dual in the sense that there are no two, that is to say, the perception of a locus of existence as the individual which is the experiencer and observer is a mere illusion, in itself a radiance of primordial awareness contracted into the experience of an individual observer. There is however also no oneness, or one thing. In the great expanse, free-flowing dyanamic space of the fundamental condition, not even a hit of objective thing'ness can be found to be either one or two. The teachings and 'path' of atiyoga point us to directly discover our authentic condition beyond the limitations of the dualistic conceptual vision. In this moment of pure presence where both object and subject collapse, the ever shining responsiveness and clarity of the pure ground is ever present as the great spontaneity. The sickness of effort that is mentioned in the text refers to the ideas of a causal factor for awakening and liberation, because there is no such thing. However, on the other hand, it would be a mistake to assume that liberation will just randomly occur without applying any means of discovery. In reality, the true path is a non-doing, however, in the normal conditioned state of being, individuals do not know what non-doing means. So even though there is no cause for awakening, there is an apparent unveiling that occurs through the application of the path by means of learning and contemplation in conjunction of certain skillful methods for self discovery. This is the path of Atiyoga.