(“aperture of Brahman”) An opening in the crown of the head in traditional mystical physiology, perhaps similar to the fontanel in young infants.
Although this hole normally closes up, it is commonly thought that if the leaving soul can be guided via this aperture at the moment of death, it will bring the soul's ultimate freedom (moksha).
The Katha Upanishad 6.16 has the oldest reference of this concept, and some types of yoga emphasize movements to aid in this practice.
One of the acts done during cremation is motivated by the need to open this aperture.
The heat from the fire often splits the skull, but if it doesn't, a long stick is used to smash it open in an attempt to free the soul.
