Head of all Heads
Head of all Heads (Kab). Used of the “Ancient of the Ancients” Atteehah D’atteekeen, who is the “Hidden of the Hidden, the Concealed of the Concealed”. In this cranium of the “White Head”, Resha Hivrah, “dwell daily 13,000 myriads of worlds, which rest upon It, lean upon It” (Zohar iii. Idrah Rabbah). . . “In that Atteehah nothing is revealed except the Head alone, because it is the Head of all Heads. . . The Wisdom above, which is the Head, is hidden in it, the Brain which is tranquil and quiet, and none knows it but Itself. . . . And this Hidden Wisdom . . . the Concealed of the Concealed, the Head of all Heads, a Head which is not a Head, nor does any one know, nor is it ever known, what is in that Head which Wisdom and Reason cannot comprehend “ (Zohar iii., fol. 288 a). This is said of the Deity of which the Head (i.e., Wisdom perceived by all) is alone manifested. Of that Principle which is still higher nothing is even predicated, except that its universal presence and actuality are a philosophical necessity.
Source: H.P.Blavatsky - The Theosophical Glossary