These are Crowley's two greatest mysteries. We need to study them in tandem, because Crowley insists that the Emperor's proper letter is not Heh, but Tzaddi, so it must change places with The Star.
By Crowley's reckoning, the star, Kokhav = 48 (a multiple of 12), the astrological number) or the "sphere of Venus". It represents Mercy (Gedulah or Chesed ). It also means, "strength" and "army". Forty eight divided by four is 14, the card of Temperance (or Alchemy), where we also have the angel pouring the waters. Qisar and Melech both translate as "Emperor". To continue with Crowley's reckoning, qisar would equal 371 ("Evil") and melech would equal 78 (that is, 15, or The Devil). However, if we use the ordinal value of the letters alone we get for Qisar and Melech, respectively, 60 and 33. Thirty Three is "sorrow, weeping" and a spring or fountain." Sixty is "watch-tower", excellence, sublimity, glory, pride, a Vision..." For kochav we get 28 or "Union, unity, power, and the mystic Netzach. . ." If we skip Aleph we get for Qisar and Melech, 60 and 30 ("Judah, Libra, Justice"). All of these seem appropriate enough for "The Emperor" but still do not explain why Crowley wants him to be the 17th card!
One reason that Crowley might have wanted to exchange The Emperor with Atu number 17 is so that (17 = 1 + 7 = 8) The Emperor (4) would serve as the higher exponent of Justice, which he had renamed "Adjustment" and already exchanged with Strength at 11. In his system, that places mundane authority (the Emperor) in the most subservient position and exalts Sirius (the Star) to the seat of greatest power at Atu 4. Meanwhile, Strength, now Atu 11, becomes the higher exponent of The Priestess (Atu 2), since 11 is the number of sorcery. This kind of highly rational manipulation of universal symbols is typical of Crowley's creative and very original approach to M/magic(k). The whole thing is extremely round-about and vexatious and looks like nothing so much as one of those infinitely-regressing whorls of cocaine-induced ratiocination, which were sometimes characteristic of Crowley. His paltry excuse that tzaddi is the letter that begins the word for Emperor "in many languages", is not meant to fool any serious student. It occurs only in Russian, Tsar, which is but a corruption of "Caesar."
Moreover, even if we assign the ordinal value to tzaddi (18), that translates as the notariqon of Yehi Aur ("Let there be light!"); Chai (the "living"); the antique serpent (Lucifer?); Hatred and "My Beloved". All of those seem strangely fitting for The Star, whereas "four" seems more natural to the Emperor if we think of him as the Tetragrammaton (IHVH). Apparently, that was precisely what AC wanted to avoid -- the ascription of IHVH to the Emperor.
Source: The Magician's Dictionary