One reason I haven't been posting much lately is that I've been combing through a bunch of old French books. Particularly, the Lettres Edifiantes et Curieuses to which Borges refers in "Fauna of Mirrors."
Let's review: The "Fauna of Mirrors" story opens as follows:
In one of the volumes of the Lettres edifiantes et curieuses that appeared in Paris during the first half of the eighteenth century, Father Fontecchio of the Society of Jesus planned a study of the superstitions and misinformation of the common people of Canton; in the preliminary outline he noted that the Fish was a shifting and shining creature that nobody had ever caught but that manysaid they had glimpsed in the depths of mirrors. Father Fontecchio died in 1736, and the work begun by his pen remained unfinished; some 150 years later Herbert Allen Giles took up the interrupted task. According to Giles, belief in the Fish is part of a larger myth that goes back to the legendary times of the Yellow Emperor.
I've gone through most of Giles's work (already mentioned here) and now I've gone through all but one volume of the Lettres. In the thirty-some I've gotten access to, there is no mention of a Father Fontecchio, or of fish being in mirrors and attacking our world.
I say all but one volume: I haven't been able to get number 31 yet.
Keep in mind a few things. First, my French is pretty rusty. Second, this is eighteenth-century French. Still, I think I've been pretty thorough. All the volumes of the Lettres are available on-line in searchable formats. I used the same terms for each volume search: miroir, Fontecchio, Zallinger, poisson, superstition.
I used to be certain that Fontecchio was a real guy, though I can't recall why and have no source for that. Zallinger is equally obscure. Let's see, there's reference to Zallinger (as Zallinger, P.) on the University of Pittsburgh's Borges Center site, but nothing on Fontecchio. They publish a journal devoted to Borges.
So what's the next step? I dunno.