Purusha
puruṣa · draṣṭṛThe Seer: the one watching the thoughts, which the texts insist is not the thoughts.
The third sutra says what remains when the mind's churn settles:
When the churning stops, what's left is the one who was watching it. The claim: your awareness is distinct from your thoughts, and can rest as itself.
“Then the Seer [that is, the Self,] abides in himself.”
The original Sanskrit
tadā draṣṭuḥ svarūpe 'vasthānam
The Seer rests in its own nature. Later the text sharpens the point:
The seer is intelligence only, and though pure, sees through the colouring of the intellect.
The original Sanskrit
draṣṭā dṛśimātraḥ śuddho 'pi pratyayānupaśyaḥ
Pure seeing, colored by the mind it looks through. Every time a teacher says "notice who is noticing," this is the claim being gestured at.