I begin by citing Atmananda’s Atma Nivritti:

1 Thoughts and Myself

I How can thoughts which rise and set in Me, be other than Myself?

Il When there is thought, I am seeing Myself; when there is no thought, I am remaining in My own glory.

Note that “I,” “Me,” “My own,” and “Myself” all refer to the ultimate, to our true nature.

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In the following experiment, generate a thought like “I am thinking” (X) and re-use this thought again and again.

Check, explore:

1. Is thought X permanent or impermanent? 
2. What is before and after thought X (A: Space, as it were.)
3. To whom or to what does X appear? (A: To Me, witnessing awareness.)
4. Imagine that this Me is boundless space. Then ask: In whom or in what does X appear? (A: In Me.)
5. Now zero in on X. Be gentle yet laser-like. Ask: What is X truly made of? (A: It’s made of Me, awareness.)
6. Double-check: Does X rise in Me? Yes. Does it fall in Me? Yes. Does it appear in Me? Yes. Is it made of Me? Yes. Is it anything other than Me? No.

Therefore:

• Check: When there is thought, I am seeing Myself.
• Check: And when there is no thought, I am remaining in My own glory, i.e., remaining only Myself.
• See, therefore: Whether there is thought or no thought, I abide as Myself.

Thought, as such, does not exist. Only I do.