Sri Aurobindo
Letters on Yoga
5. Planes and Parts of the Being
Fragment ID: 539
When we speak of concentrating in the heart in yoga, we are speaking of the emotional centre and that like all the others is in the middle of the body in a line corresponding to the spinal cord. The planes he refers to are four centres: (1) crown of head or higher mental centre, (2) between the eye-brows or centre of will and vision, (3) throat or centre of externalising mind, and (4) heart, i.e. mental-vital, emotional centre with the psychic behind it (the soul, Purusha in the heart).
Chitta as opposed to Chit or Vijnana is only the basic mind-life consciousness out of which rises the stuff of (ordinary) thoughts, feelings, sensations etc. The Force which he feels is something quite different; it is the larger force exceeding the individual, and when one feels it in its fullness, it is experienced as the cosmic force or something of the cosmic force or else the Divine Force from above, according to its nature.
His mind is not yet ready for the action of the greater force, because it is full of mental notions and activities and it is for 
this reason that heat is generated in the friction between the two; when the other force withdraws and no longer tries to lay hold of the brain, then the personal mind-action feels released (that is the reason for the sense of coolness) and goes about its ordinary notions. It is only in a silent (quiet, not necessarily empty) mind that the greater force can be received and work upon the system without too much reaction and resistance.
Current publication:
Sri Aurobindo. Letters on Yoga // SABCL.- Volume 22. (≈ 28 vol. of CWSA).- Pondicherry: Sri Aurobindo Ashram, 1971.- 502 p.
Other publications: