A quiet mind.

"Keep quiet, undisturbed, and the wisdom and the power will come on their own. You need not hanker. Wait in silence of the heart and mind. It is very easy to be quiet, but willingness is rare. You people want to become supermen overnight."
- Nisargadatta


"A quiet mind is all you need. All else will happen rightly once your mind is quiet."
- Nisargadatta


"The only way you will ever awaken is through silence, not through analyzation of facts. Not by sorting out good and bad, but through simple silence, letting go. Letting go of all thoughts, all the hurts, all the dogmas and concepts. Letting go of these things daily. Whichever method suits you use it."
- Robert Adams


"Simply keep quiet. Do not do anything and it will happen. Abandon even the intention to get something in the next moment. Do not even make the distinction between "this moment" and "the next moment". Then something will happen instantaneously."
- Papaji