Yoga Sutras of Patanjali translated by Yogi Kalinath - Chapter 4, Verse 20
Pada 4, Sutra 20
And the impossibility of cognizing both at the same time.
The Self, the Seer, the Eternal Witness Within is self-luminous and is the awareness of awareness itself.
It alone is aware of any modifications in consciousness while our individual consciousness can only be aware of either the Self or the object perceived but not both at the same time. The individual consciousness habitually gets drawn to external objects of reference through the senses or becomes absorbed in the incessant movements of the mind. Rarely does it truly turn inwards peeling away the layers of the mind to encounter the true self, the Self of true selves.
Who is aware of who?