The Gardnerian Book of Shadows, by Gerald Gardner, at sacred-texts.com
It is important to work naked from the start, so it becometh as second nature, and no thought of "I have no clothes" shall ever intrude and take your attention from the work. Also, your skin being so accustomed to unconfinement, when power is given off the flow is more easy and regular. Also, when dancing you are free and unconfined. . . . And the greatest of all, the touch of the body of your beloved thrills your inmost soul, and so your body gives out its utmost power; and then it is most important of all that there is not the slightest thing to divert the attention, for then the mind must seize and mold the power generated, and redirect it to the desired end with all the force and frenzy of the imagination. It has been said that no real knowledge may be gained our way, that our practices are such that they can only lead to lust; but this is not really so. Our aim is to gain the inner sight, and we do it the most natural and easy way. Our opponents' aim is ever to prevent man and woman from loving, thinking that everything that helps or even permits them to love is wicked and vile. To us it is natural, and if it aids the Great Work it is good. 'Tis true that a couple burning with a frenzy for knowledge may go straight to their goal, but the average couple have not this fire. We show them the way, our system of props and aids (i.e., magic ritual). A couple working with nothing but lust will never attain in any case; but a couple who love each other dearly should already be sleeping together, and the first frenzy of love will have passed, and their souls will already be in sympathy. If the first time or two they do stay a while to worship Aphrod ite, 'tis only a day or two lost, and the intense pleasure they obtain only leads them again to the mysteries of Hermes, their souls more attuned to the great search. Once they have pierced the veil they will not look back. This rite may be used as the greatest of magics if it be done with both partners firmly fixing their minds on the object and not thinking of sex at all. That is, you must so firmly fix your mind on your object that sex and all else are naught. You inflame your will to such an extent that you may create a strain on the astral such that events happen.