Tau

Taking each letter of Tau in full we get 418.

Tau + Vau + Vau + Vau or the Cross ("the Sign of Light", "Mine is the symbol of Osiris") + the Nail (thrice).

The Dagger is Mercury: it is used to calm too great heat, by the letting of blood; and it is this weapon which is plunged into the side or heart of the Magician to fill the Holy Cup. Those faculties which come between the appetites and the reason are thus dealt with.

Students of the gospel will recollect that in the martyrdom of Christ these three were used, the dagger being replaced by the nails.

the Dagger expresses the determination to sacrifice all

-excerpts from Book IV part. 2 chpt. IV

R. Amen! I am willing to be slain.
Verily I shall rise again!

http://www.luckymojo.com/crowley/000tfritual.txt

Its interesting that this isn't noted in Liber D or Liber LVIII. See also this.

"It is Thou!"