But historically, claims of actual eternal flames go back a very long way: in my book, I mentioned briefly that many in the Renaissance believed a "perpetual light" burned in the Temple of Vesta in Ancient Rome. Leon Battista Alberti's 1450 book "Momus" mentions (though admittedly in a fictional context) a "perpetual flame, tending itself even though no material is laid under it and no liquid poured over it", Giovanni Battista Della Porta documented many attempts at reproducing eternal flames in his Natural Magic in XX Books, while in his libro architettonico Antonio Averlino described a continuously-burning candle he saw in Sant Maria in Bagno. Another related story concerns Abbot Trithemius, who allegedly sold two "unquenchable eternall lights" to Emperor Maximilian I for 6000 crowns.
I thought this was one of those things for which there was unlikely to be any significant literature: I'd collected all the pieces together from scattered footnotes. However, recently I was inspired by Archer Quinn's, ummm, perpetual ranting to properly read through Kevin Kilty's well-known page on perpetual motion. All good stuff: and he even mentions eternal flames!
Kilty, who seems to have derived his information on this subject from Arthur Ord-Hume's 1977 book "Perpetual Motion: history of an obsession", mentions that:-
"Fortunio Liceti (1577-1657) made a lifelong study of these lamps, so many of which were supposedly found in old tombs, vaults and temples. Ord-Hume spends several pages examining ways to explain the observation of perpetual lamps. This is giving too much serious attention to a fantasy. It is likely that no one ever observed any such lamp."
(Though I should of course point out that Averlino claimed to have observed an eternal flame). Fascinating! I was not aware of Fortunio Liceti's connection with eternal flames, and so rushed to buy Ord-Hume's book as quickly as I could. I shall continue this thread when it arrives...