Nisargadatta Maharaj
From Wiki:
"My Guru ordered me to attend to the sense ‘I am’ and to give attention to nothing else. I just obeyed. I did not follow any particular course of breathing, or meditation, or study of scriptures. Whatever happened, I would turn away my attention from it and remain with the sense ‘I am’. It may look too simple, even crude. My only reason for doing it was that my Guru told me so. Yet it worked!"
Following his guru’s instructions to concentrate on the feeling "I Am", he utilized all his spare time looking at himself in silence, and remained in that state for the coming years, practising meditation and singing devotional bhajans
