The following is a very interesting and useful section from the 8th century Bon Dzogchen text called the “Six Lamps”. It describes the three aspects of the Base (Zhi) in a very different style from the Nyingma texts.
THE NATURAL STATE OF THE BASE
As to the explanation of the natural state of the Base, know that it is expressed according to three (themes, namely,) The Universal Base (Zhi), Awareness (rigpa), and the mind (sem).
The Universal Base (Zhi)
As for the Universal Base, the Pure and Perfect Mind, It is the empty Clear-Light, uncorrected and unaltered. Its Great Primordial Purity or Absolute Body is totally immaculate and unaffected by limitations. Its Spontaneous Nature or Body of Perfection Is entirely perfect, fully perfect, totally perfect. Its undetermined and neutral Emanation Body Arises in all kinds of impartial marvels. (Yet this Base) is not divided into individual (partialities): Just like the sky entirely (embraces) manifested existence, it encompasses the whole of saṃsāra-nirvāṇa. Its unique celestial Clarity embraces everything in a clear sky free from partialities. Everything arises from its unique, great Expanse, An empty Expanse that has no dimension. Everything abides in its unique and great Space, an equal Space that is neither high nor low. Thus it is called the “Pure and Perfect Mind,” Which is explained as being threefold according to the conventional meaning, while it is undifferentiated according to the real meaning, abiding as the Single Great Thiglé. Samaya!
The “Wisdom of Awareness” is the Awareness (rigpa) arising from within the expanse of the Universal Base in the same way the sun (shines) in the expanse of the sky. Luminous in its Essence while empty in its Nature, this knowing Awareness is free from concepts. In it arises the threefold dynamism of visions, namely that of sounds, lights, and rays: It arises as lights in the clear sky, (Reverberates as) self-arisen sounds from within the empty Expanse, And projects itself as the rays of nondual Awareness. This (dynamism, tsal) is known as that of the “manifested objects.” (Yet,) these objects and Awareness are not separated, since they are linked as an inseparable pair, which is called the Wisdom of Awareness, the Universal Base of the continuity of wakeful Awareness, the Base of the Qualities of the Mirror-Like Wisdom, the Consciousness of the Universal Base or Base of propensities. In its total and unmixed perfection, the (Wisdom) of Awareness arises in the mental continuum of each (being). The Universal Base is neutral and free from conceptions, And even though its Essence is primordially pure and immaculate, it still abides as the Base of both saṃsāra and nirvāṇa, defects and qualities. (Thus,) through the link between lights and Awareness, It becomes the Base of (Buddha) Bodies and (ordinary) bodies. Through the link between sounds and Awareness, It becomes the Base of the Speech (of the Buddhas) and (ordinary) speech. And through the link between rays and Awareness, It becomes the Basis of the (Buddha) Mind and the (ordinary) mind. Samaya!
The Mind (sem)
As to the “ordinary thinking mind,” even though the King of wakeful Awareness is free from conceptions, It is still the Base in which arises the diversity of thoughts and recollections: (Therefore,) just like luminous rays (emanating) from the dynamism of the sun, the mind (sem) arises from the dynamism (tsal) of Awareness. The various thoughts and recollections are then involved with objects and the six associations arise as the dynamism (tsal) (apprehending) the six objects (of the senses). This is called the “thinking mind.” It is named “recollection” because it remembers and understands (things) and “mind” since it is involved with objects. Samaya!“
“The Universal Base is like the extent of the sky, Awareness is like the quintessence of the sun, the mind is like the luminous rays of the sun”