“[M]edieval readers most likely would be uncomfortable reading a book in a flat position, because the way they most often encountered books set out to be read was propped up on another book or on a slanted surface not unlike a modern lectern or music stand. Indeed, the word “lectern” comes from the Latin verb legere, “to read,” and even a modern lectern has a sloped surface to hold books or notes.”

—Hentry Petroski, The Book on the Book Shelf, 1999.