The Malleus Maleficarum by Kramer and Sprenger, 1489, Excerpts
There are five ways in which the devil can impede the act of generation, and they are more easily operated against men. God allows the devil more power over that act than over other human acts, because of its natural nastiness, and because by it the first sin was handed down to posterity.
For the devil, being a spirit, has by his very nature power, with God's permission, over a bodily creature, especially to promote or to prevent local motion. So by this power they can prevent the bodies of men and women from approaching each other; Secondly, the devil can inflame a man towards one woman and render him impotent towards another; Thirdly, he can disturb the apperception of a man or a woman, so that he makes one appear hideous to the other; for, as has been shown, he can influence the imagination. Fourthly, he can suppress the vigour of that member which is necessary for procreation; just as he can deprive any organ of the power of local motion. Fifthly, he can prevent the flow of the semen to the members in which is the motive power, by as it were closing the seminal duct so that it does not descend to the genital vessels, or does not ascend again from them, or cannot come forth, or is spent vainly.
In conclusion we may say that there are five remedies which may lawfully be applied to those who are bewitched in this way: namely, a pilgrimage to some holy and venerable shrine; true confession of their sins with contrition; the plentiful use of the sign of the Cross and devout prayer; lawful exorcism by solemn words, the nature of which will be explained later; and lastly, a remedy can be effected by prudently approaching the witch.