Via the Light Reader, a note on an annotated First Folio (from The Guardian):
"Defacing some of the pages, but probably raising the value, are the marginal scribbles of one of its first readers. In brown ink this early Shakespeare devotee marked interesting passages with circles or wavy lines, often scrawling, like some early A-level candidate, 'joy', or 'wit', or 'time', or, most commonly of all, 'simile'."
In Pnin there is this droll aside, part of the bravura opening to chapter six:
"Again in the margins of library books earnest freshman inscribed such helpful glosses as 'Description of nature' or 'Irony'; and in a pretty edition of Mallarmé's poems an especially able scholiast had already underlined in violet ink the difficult word oiseaux and written above it 'birds.'"
(Significantly, while typing this out, I nearly wrote violent for violet.)