The serpent fire starts at the sex organs, proceeds to the solar plexus as the most important ganglion of the sympathetic nerve system, continues up the spine and ends in the frontal brain. These are the progressive stations of its passage when governed by will and directed by aspiration. The first sign is an increase of the heat of the body, sometimes resulting in perspiration. The second sign of its movement is a trembling or agitation in the navel region of the abdomen as the solar plexus is entered and the magnetic centre within it begins to open. The third sign is an unconscious drawing of deeper breaths. The last sign is a sensation of added force on all levels--physical, emotional, mental, and mystical.
-- Notebooks Category 5: The Body > Chapter 8: Kundalini > # 43