In the Zohar the first chapter of The Book of Concealed Mystery is dedicated to a complete description of him. There we are told that his skull has as its primary substance the light of the En-Sof, & contained wthin that a crystalline dew. The brightness of his skull, we are told, extends into 40,000 worlds superior to this one, & the interior of it contains an additional 13,000 myriads of worlds. The dew in which these worlds float flows down from his head & is the elixir which reawakens the dead for the world to come, the manna of heaven. It is this crystalline dew, white in color, in the skull of the Macroprosopus which the Kabbalists believe is referred to in Exodus xvi, 14: And when the dew that lay was gone up, behold, upon the face of the wilderness there lay a small round thing, as small as the hoarfrost on the ground.
The membrane of the brain of Macroprosopus has an outlet which leads to the worlds below, the Sefiroth below, so that His brain can send out along thirty-two paths a shining white emanation. It is for this purpose that the skull has a small hole at its base. This refers us to the thirty-two paths mentioned in the opening stanza of the Sefer Yetsirah: Jehovah, through thirty-two paths, engraved His name. The Kabbalists also see in this idea the meaning of Genesis ii, 10: And a river went out of Eden to water the garden.
His hair, which is made of a substance as fine & as white as wool, is composed of 7,500 hairs which radiate the lights of the fountains contained within each of them into 410 worlds (410 being the numerical value of the word 'holy'.)
Of his one eye which is visible to us, the Kabbalists, citing Psalm cxxi, 4 (Behold, he that keepeth Israel shall never slumber nor sleep.), say it is eternally open & that if it should close but for a fraction of a second nothing could exist. It is for this reason that the Macroprosopus' eye is depicted as being lidless.
From his nostrils, which are described as being the size of enormous galleries, the spirit issues forth to the lower worlds.
His beard, as white as the wool of his hair, is divided inte thirteen paths - thirteen being the number expressive of unity. The Book of the Greater Assembly in the Zohar dedicates one chapter to each portion of his beard.
One cannot help recalling, while holding this picture of Macroprosopus in mind, a section from The Book of Daniel in the Old Testament where we are told he saw in vision the Ancient of days whose garment was white as snow, & the hair of his head like the pure wool: his throne ... like the fiery flame, & his wheels as burning fire." (Daniel vii, 9.)