Anyway, I reread it the other day, and I was struck by this passage:
The idea that one person can gain unnatural power over another is not a new one. Enchantment in particular is a very ancient and widespread concept, if rather diffusely defined, its effects ranging from the wholly physical to the predominantly mental. These include bodily transformations, such as those imposed by Homer’s Circe; loss of physical control, as when Prospero uses the power of suggestion to disarm Ferdinand in The Tempest; deception of the senses, for example the glamour cast by fairy magic; manipulation of the affections, as with the love potions that throng romance and folk tale; and suppression of mental faculties such as memory. It is however rare to find pre-modern works that conceive of enchantment in terms of the absolute and involuntary enslavement of a person’s will. During the nineteenth century, however, this kind of mind control became widely associated with mesmeric (later, hypnotic) power, culminating in popular literature in the appearance of such sinister hypnotists as Svengali, Dominick Medina and Fu Manchu.
The fact is that I couldn't find any pre-Mesmer examples of that kind of enslavement, but of course I didn't want to give a hostage to fortune by saying that there weren't any. And it does seem implausible that none exists - but where?