"the number six is represented in the Qabalah by two triangles which form the seal of Solomon when they are brought together and given a common center." (The Mysteries of the Qabalah, by French Freemason and Kabbalist magician, Eliphas Levi).

Therefore, in Qabbalistic numerology, the number 66 is equivalent to the following ideograph:

According to Albert Churchward, the Freemason who authored The Arcana of Freemasonry, the double-hourglass symbol, as pictured here, represents the god of the Masonic Brotherhood, G.A.O.T.U., i.e., Grand Architect Of The Universe: "The triangle was sacred on account of its representing Heaven. The Primary Triangle originally represented Set, but when Horus took the place and attributes of Set, he became God of the Celestial North. Their two symbols were afterwards blended, as fig. 23. This form was sometimes doubled, as Fig. 20., and was then the most sacred sign amongst the old Brotherhood." (Churchward, The Arcana of Freemasonry)

So, in Judeo-Freemasonry, the number 66 is evidently considered a kabbalistic equivalent of the Seal of Solomon, or the hexagram, because, according to Churchward, as well as many other Masonic scholars, the hexagram likewise signifies T.G.A.O.T.U., or the Grand Architect of Freemasonry. David Cherubim, an initiate of the Golden Dawn secret society, claims, among others, that the hexagram is equivalent to the number 666. (See external link: http://thelemicgoldendawn.net/documents/hexagram.htm )