"In short, my grandfather taught me the Zulu version of what is called in English, "meditation". How to breathe softly and gently like a whisper until you feel something like a hot coiled snake bursting through the top of your head - a fearsome thing that is known as the umbilini. This umbilini, my grandfather told me, is the source, the primal source of the sangoma’s powers. A sangoma must be able to summon this umbilini at will through the beating of the drum and through meditation, very, very deep meditation."
Vusamazulu Credo Mutwa - Zulu Shaman p.13
From African Ancestral Voices: Esoteric African Knowledge.