In Ulladu Narpadu Anubandham Bhagavan Sri Ramana Maharishi mentions the three paths: self-enquiry, observation of breathing, and diving within the heart.
The result of following these three paths is the same:
Self-realisation. And it can also be said that the three paths are also the
same, although at first sight the description of them makes it sound as if
three totally different techniques are being described.
Bhagavan said, ‘Do self-enquiry. Find out who you really
are. When you are totally absorbed in this problem, this enquiry will lead you
to the Self.’ Some people, though, said that they found this very hard, or they
said that this method somehow didn’t appeal to them. Bhagavan would sometimes
tell such people to watch the breath, to see where it arose. Bhagavan always maintained
that mind and breath arose in the same place, so focusing attention on the
source of the breath is really the same
as focusing attention on the source of the mind through
self¬ enquiry. The third option is diving within. This is not a separate path.
It is just another description of what happens when you follow self-enquiry, or
when you find the source of the breath through intense observation. ‘Diving
within’ means putting your whole mind on the Self. When the one-pointed
intensity to discover the Self is there, diving in happens and the mind goes back
to its source and merges there.
The diving within doesn’t happen by itself. You have to go on
making an effort until the point where you become totally effortless. Up till
that moment your effort is needed. The mind only gets dissolved in the Self by
constant practice. At that moment the ‘I am the body’ idea disappears, just as
darkness disappears when the sun rises.