Talking of M.R. James (and who isn't, I'd like to know?) here is an excellent blog item on the inspiration behind one of his stories. 'Casting the Runes' sees the hapless victim of sorcery handed a paper in the British Museum's reading room. The Museum was so pleased with the tale that it bought the MS in 1936.
In the item you can take a look at the document - a cartulary, i.e. a collection of medieval charters - that poor Alfred Dunning is studying.
And here is the MS of the story wot Monty wrote. Even scrappier than mine, which is saying something.