The thought 'who am I?' will destroy all other thoughts...
Ramana Maharshi (1879-1950) is one of the most influential spiritual master till date. His awakening happens when his was 16 years old.
In his words, "It was in 1896, about 6 weeks before I left Madurai for good, that this great change in my life took place. I was sitting alone in a room on the first floor of my uncle's house. I seldom had any sickness and on that day, there was nothing wrong with my health, but a sudden violent fear of death overtook me. There was nothing in my state of health to account for it nor was there any urge in me to find out whether there was any account for the fear. I just felt I was going to die and began thinking what to do about it. It did not occur to me to consult a doctor or any elders or friends. I felt I had to solve the problem myself then and there.
The shock of the fear of death drove my mind inwards and I said to myself mentally, without actually framing the words: 'Now death has come; what does it mean? What is it that is dying? This body dies.' And at once I dramatised the occurrence of death. I lay with my limbs stretched out still as though rigor mortis has set in, and imitated a corpse so as to give greater reality to the enquiry. I held my breath and kept my lips tightly closed so that no sound could escape, and that neither the word 'I' nor any word could be uttered.
'Well then,' I said to myself, 'this body is dead. It will be carried stiff to the burning ground and there burnt and reduced to ashes. But with the death of the body, am I dead? Is the body I? It is silent and inert, but I feel the full force of my personality and even the voice of I within me, apart from it. So I am the Spirit transcending the body. The body dies but the spirit transcending it cannot be touched by death. That means I am the deathless Spirit.' All this was not dull thought; it flashed through me vividly as living truths which I perceived directly almost without thought process. I was something real, the only real thing about my present state, and all the conscious activity connected with the body was centered on that I.
From that moment onwards, the "I" or Self focused attention on itself by a powerful fascination. Fear of death vanished once and for all. The ego was lost in the flood of Self-awareness. Absorption in the Self continued unbroken from that time. Other thoughts might come and go like the various notes of music, but the I continued like the fundamental sruti note, a note which underlies and blends with all other notes." He adviced spiritual seekers and devotes to inquire about the nature of one self by asking "Who am I". This inquiry about oneself has been his main instruction. "The thought 'who am I?' will destroy all other thoughts, and like the stick used for stirring the funeral pyre, it will itself be burnt up in the end. Then, there will be self-realization. When other thoughts arise, one should not pursue them but should diligently inquire: ‘To whom do they occur?’ It does not matter how many thoughts arise. As each thought arises, one should inquire with alertness, “To whom has this thought arisen?” The answer that would emerge would be “to me”. Thereupon if one inquires “Who am I?” the mind will go back to its source; and the thought that arose will subside."
The Love of Ramana Maharshi for Arunachala revived all texts and practices around the holy mountains. But he also emphasize his greatest power and Grace. ""Kailasa is the abode of Shiva; Arunachala is Shiva Himself. " He also said in his poetry:" 'O Arunachala, you root out the ego of those who think of you in the heart as ''Arunachala'''.
Ramana is the embodiment of Arunachala, a pure incarnation of the self.
For more: http://www.sriramanamaharshi.org/