Edge-notched cards

That great lover of paper ephemera Nicholson Baker would likely note all the extraneous, but scrutinizable data left on the edges of these cards in their handling and sorting—an unrecorded search history in the sections of card-edge gone dark and felty with repeated sorts

Edge-notched cards were invented in 1896. These are index cards with holes on their edges, which can be selectively slotted to indicate traits or categories, or in our language today, to act as a field. Before the advent of computers were one of the few ways you could sort large databases for more than one term at once.

a more than 95 theses post by Alan Jacobs