If the mind becomes absorbed in the Heart, the ego or 'I', which is the centre of the multitude of thoughts, finally vanishes and pure Consciousness or Self, which subsists during all the states of the mind, alone remains resplendent.
It is this state, where there is not the slightest trace of the 'l'-thought, that is the true Being of oneself. And that is called Quiescence or Mouna (Silence).
#SriRamanaMaharshi