D : Please give me some more details about Heart and its movements.

M: Heart is the seat of knowledge and the knot of ignorance.
It is represented in the physical body by a hole smaller than the smallest pin-point, which is always shut.
When the mind drops down in 'Kevala Nirvikalpa', it opens but shuts again after it. When sahaja is attained it opens for good.
The knot which ties the insentient body to the consciousness, which functions in it is the 'knot of ignorance'. That is why when it is loosened temporarily as in Kevala Nirvikalpa when there is no body consciousness.

I used to feel the vibrations of the Heart, which resemble those of a dynamo, even in school.

When I developed rigor mortis many years ago in Tiruvannamalai, every object and sensation disappeared, except these vibrations.
It was as if a dark screen was drawn before my eyes and shut the world completely from me, but of course I was all along conscious of the Self, with a vague feeling that some one was crying near me.
This state continued till just before I regained physical consciousness, when I felt something rush from the Heart to the left chest and re-established life in the body.

A sudden fear, sudden joy, or a shock makes the Heart vibrate very forcefully, so that it can be felt by anyone who pays attention to it.
Otherwise it is felt only in Samadhi .

Essential Concepts in the Yoga of the Spiritual Heart

1. The Spanda
   
2. The Witness Consciousness
3. The Open Attention
   
4. Sublimation
   
5. The Sahaja
   
6. Advaita Vedanta
   
7. Atman
   

Glossary
Suggested Reading
Shankaracharya