To echo Dan's comment, Bob, thanks for your message and the Google books link. It's always illuminating to track down the original sources, even in trustworthy works such as Day's. Though, practically speaking, I doubt I'll be needing a tying method for the butterfly which requires both ends.
I followed a thread like this to the 1931 Finnish scouting knot manual,
Solmukirja, which is cited as the first illustration of the Constrictor. It led me to an interesting and surprisingly extensive early knot book. If only I could read suomi...
I came up empty in my later search for the Cornell "Reading Course" pamphlet Ashley refers to as the earliest source for the Farmer's Loop, but that was a few years ago and Google and libraries in general have done a lot of work since then. I should try again.
Smart and cautious formulation by Wright & Magowan:
..it might be rash to claim that they never have been used before..
Other knot authors are less humble.
Yes, but not all. I appreciated that in the Quibble(tm) GB quoted two very scholarly, though obscure compared to Ashley, knot authors. I think it's really too bad some of the most well-researched knotting works have passed out of print (e.g.
Day's Quipus and Witches' Knots) or are otherwise difficult or prohibitively expensive to procure (e.g.
History and Science of Knots). I've been meaning to reply to the Quibble thread -- and this comment would probably best go there... But as I'm arriving to the party a little late, the more I read of that thread the longer my potential response keeps growing in my head.