Aleister Crowley:

Poet, Expert Mountaineer, and infamous Occultist.
He was at one time known as "The Wickedest Man in the World".
There are volumes of information on Mr. Crowley on the Internet and in bookstores, so if you really want to find out more about the man, I would suggest that you take it upon yourself to do the research.
Weakness, a lack of faith in your own self, or any "hang-ups" that you might have regarding religion, are reasons NOT to study Crowley and his system of Magick.

I feel the need to state now, for the record, that I am a Christian and have MY relationship with God. Just remember this: Christ once said, "Judge not, lest ye be judged..." My relationship with God is based on fundamental Christianity. I may have some "strange" beliefs that coincide with my Christianity, but those are between Jehovah and myself.

I have studied various aspects of Occultism for several years, only for the knowledge and certain insights.

I strongly advise anyone who has, even the smallest of doubts concerning your own system of beliefs, to avoid the study of Occultism until you have found the faith in God that is needed to study such matters.

YOU HAVE BEEN WARNED.

One of my favorite poems by Crowley is called "Aha".
This is only part of it, (a very long piece it is), published in 1919.

"AHA"

There are seven keys to the great gate,
Being eight in one and one in eight.
First, let the body of thee be still,
Bound by the cerements of will,
Corpse-rigid; thus thou mayest abort
The fidget-babes that tease the thought.
Next, let the breath-rhythm be low,
Easy, regular, and slow;
So that thy being be in tune
With the great seas's Pacific swoon.
Third, let thy life be pure and calm,
Swayed softly as a windless palm.
Fourth, let the will-to-live be bound
To the one love of the profound.
Fifth, let the thought, divinely free
From sense, observe its entity.
Watch every thought that springs; enhance
Hour after hour thy vigilance!
Intense and keen, turned inward, miss
No atom of analysis!
Sixth, on one thought securly pinned
Still every whisper of the wind!
So like a flame straight and unstirred
Burn up thy being in one word!
Next, still that ecstasy, prolong
Thy meditation steep and strong,
*Slaying even God, should He distract*
Thy attention from the chosen act!
Last, all these things in one o'erpowered,
Time that the midnight blossom flowered!
The oneness is. Yet even in this,
My son, thou shalt not do amiss
If thou restrain the expression, shoot
Thy glance to rapture's darkling root,
Discarding name, form, sight, and stress
Even of this high consciousness;
Pierce to the heart! I leave thee here:
Thou art the Master, I revere
Thy radiance that rolls afar,
O Brother of the Silver Star!

-Aleister Crowley (1875-1947)

(* I must add that the slaying of God is obviously impossible, thus entirely, metaphorical. Crowley was merely stating the importance HE placed on achieving a certain state of mind and soul.)