Ramana Maharshi

 My Comment: If we know 'who am I?", we know it all. 

AI Baba: 

Ramana Maharshi’s core teaching is Atma-vichara or Self-enquiry, the direct path to Self-realization by constantly focusing on the "I"-thought to discover the source of the mind. He taught that the ego is a fiction and that our true nature is silent, blissful consciousness (Self), realized when the mind merges into its source. 

Key elements of his teachings include:

Who Am I? (Self-enquiry): When thoughts arise, instead of following them, one should ask, "To whom did this thought arise?" and focus on the source of the "I".

Self-Realization: Realization is not gaining something new, but removing the "I am the body" illusion and simply being your true self.

The Mind is a Myth: The mind is just an "I"-thought. When it stops focusing on external objects and looks within, it dissolves into the Self.

Surrender & Grace: Surrender the ego to the Divine (or the Self), as the "I" is the ultimate obstacle.

Silence: Silence is the loudest teaching, removing the misconceptions of the mind. The Self is found in the heart, in a state of pure awareness without thought.

Meditation vs. Activity: He encouraged sustaining the "I" awareness constantly, not just during meditation. 

Ramana Maharshi advised holding onto the "I" thought as a way to find the Self, which is our real nature.