Egyptian Magic in Egyptian Magic by Florence Farr.
“the hawk-soul is only represented as resting upon the KA of the King or Queen. It is called the Royal Soul. The Human-headed hawk hovers over the mummies of great initiates and doubtless represents the soul after the incarnation had ceased; its human head is the symbol of true quintessence of the human individuality which the bird bears to the Abode of Blessed Souls.” [via]