Two of the presenting professors and one of the attendees.

The young lady on the left (an art history prof. @ M.I.T.!) gave a paper about an 18th Century collector and dealer of drawings. His name was Mariette, and he was famous for his blue mats. Also famous for the impressive ability to split a sheet of paper down the gizzard, so that a single sheet with a recto and verso side could be divided into two separate pieces of paper--quite a feat!

Here's a blue mat of his (landscape by Claude Lorrain, 1645)

(Claude's really brushin' that breakfast!)

In addition to all this fun, Mariette would sometimes cut up the old master drawings that he acquired, sometimes he'd "restore" them by darkening their lines, or adding lines and even adding highlights and wash to make them look more "finished."

For this he is known as "Naughty Marriette."