The Philosophy of Natural Magic, by Henry Cornelius Agrippa, L. W. de Laurence ed. , at sacred-texts.com
Fascination is a binding, which comes from the spirit of the witch, through the eyes of him that is so bewitched, and entering to his heart. Now the instrument of fascination is the spirit, viz., a certain pure, lucid, subtile vapor, generated of the purer blood by the heat of the heart. This doth always send forth, through the eyes, rays like to itself. Those rays, being sent forth, do carry with them a spiritual vapor, and that vapor a blood (as it appears in swollen and red eyes), whose rays, being sent forth to the eyes of him that looks upon them, carry the vapor of the corrupt blood together with itself;
by the contagion of which it doth infect the eyes of the beholder with the like disease. So the eye, being opened and intent upon any one with a strong imagination, doth dart its beams (which are the vehiculum of the spirit) into the eyes of him that is opposite to him; which tender spirit strikes the eyes of him that is bewitched, being stirred up from the heart of him that strikes, and possesseth the breast of him that is stricken, wounds his heart and infects his spirit. Whence Apuleius saith, "Thy eyes, sliding down through my eyes into mine inward breast, stir up a most vehement burning in my marrow." Know, then, that men are most bewitched when, with often beholding, they direct the edge of their sight to the edge of the sight of those that bewitch them; and when their eyes are reciprocally intent one upon the other, and when rays are joined to rays and lights to lights, the spirit of the one is joined to the spirit of the other and fixeth its sparks. So are strong ligations made, and so most vehement loves are inflamed with only the rays of the eyes; even with a certain sudden looking on, as if it were with a dart or stroke, penetrating the whole body, whence then the spirit and amorous blood, being thus wounded, are carried forth upon the lover and enchanter, no otherwise than the blood and spirit of the vengeance of him that is slain are upon him that slays him. Whence Lucretius sang concerning those amorous bewitchings
So, great is the power of fascination, especially when the vapors of the eyes are subservient to the affection. Therefore witches use collyries, ointments, alligations, and such like, to affect and corroborate the spirit in this or that manner. To procure love they use venereal collyries, as hippomanes, the blood of doves, or sparrows, and such like. To induce fear, they use martial collyries, as of the eyes of wolves, the civet cat, and the like. To procure misery or sickness, they use Saturnine things, and so of the rest.
155:* Again, in speaking of the power of Venus, the goddess of peace, over Mars, the god of war, he says: