This is the lede in a review of Demon Lovers: Witchcraft, Sex, and the Crisis of Belief by Walter Stephens, from the NYRB:

Imagine this world: one in which many of the normal-looking people on the street consist not of flesh and blood, but of condensed air. They can move, and even speak. Though they cannot produce semen, they can have sex—which they strongly prefer to do in the most conventional way. Since they can take either female or male form, they harvest semen from human males, which they store up for later injections into human females. When touched—so one informant explains—they feel ‘very similar to flax or cottonwood that has been bundled and densely packed’—not the most attractive imaginable physique. But their ‘pleasing faces,’ adept wooing, and enormous virile members, which ‘fill up the most secret parts’ of the women they sleep with, make them irresistible: ‘probably they can stimulate something very deep inside…by means of which these women have greater pleasure than with men.’ No wonder, then, that women are so often seen in the woods and fields, lying on their backs, legs in the air, making the motions and noises appropriate to copulation: they are having intercourse with their invisible demon lovers.

Pretty racy stuff, eh? Kinda makes you wish you had access to the rest of the review, or a handy copy of the book itself!

And people say history is boring.