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I stumbled across a passing reference to an 18th century work that explained the secret to a long life is inhaling the breath of young girls. Not entirely sure whether this would be more strange or creepy I looked it up and the 1771 English translation is available (which reveals the author specified young women or men not girls). Turns out that the work is satirical though its targets are now so obscure that its original intent is mostly gone. And why am I not surprised that Baring-Gould was here before - did he read everything?
This edition and the others on Open Library uses the long-S which is easy enough to read but just tricky enough that it's not always worth that little effort. An 1885 edition with modernized spelling is available on Hathi Trust (though it's missing the Preface complaining about the necessity of a preface). Neither has the illustration mentioned by Baring-Gould.
The English translation is by Scottish historian (the DNB calls him a "miscellaneous writer") and buddy of Dr. Johnson John Campbell (1708-1775). Like his fellow Scot Urquhart, Campbell was apparently quite free in his translation, adding extra material and altering others - though unlike Urquhart he toned down or removed potentially offensive passages. (There doesn't appear to have been any other translation into English.) According to Boswell, Johnson in 1763 said Hermippus Redivivus is "a curious history of the extravagancies of the human mind" though he was under the impression that Campbell wrote it. Robert Southey also appears to have read it - at any rate he owned a copy and mentions it in a letter as "that strangest of strange books" (March 11, 1814).
Historian Anna Marie Roos wrote the most extensive piece on Hermippus Redivivus which covers in admirable detail the book's history, its author and the medical background that he was satirizing.
