Sadhana, the discipline, is only this: the knowledge which is dwelling in this body, the quintessence of these three gunas — the knowledge “I am,” “I am that” — this is the initial step.

You must be one with it, you must abide in that only. You have to think “I am not the body but I am that formless, nameless knowledge indwelling in this body; that (is) `I am’.” When you abide sufficiently long in this state, whatever doubts you may have,  that knowledge “I am” itself will sprout out with life and meaning for you, intended for you only, and everything will become clear.

No external knowledge will be necessary.

~ Nisargadatta