Sri Bhagavan Ramana Maharshi was one the greatest saints of India, from the non-duality (or Advaita Vedanta) tradition, although he respected all other yoga traditions.
He followed the path of knowledge, or Jnana Yoga, through self-analysis (self-inquiry) and reached sublime heights by eliminating false identifications with the body, senses and mind.
Spiritual Teachings of Ramana Maharshi presents his teachings in a question and answer format.
Ramana taught that the mind will merge only by self-inquiry and that the thought, "Who am l?" will destroy all other thoughts and finally destroy itself, too. If you inquire "Who am I?" the mind will eventually return to its source, which is God within you, and you will experience non-duality or Liberation.