Arthurian Euhemerism

[steepholm]

I wonder who was the first person to suggest that the story of the sword in the stone might be an allegory about the discovery of iron smelting? They were very fond of interpreting classical legends that way in the Renaissance, but I never heard of the method being applied to anything Arthurian. I'd guess it was a 19th or 20th-century notion, but it would be good to trace it to source.