Quarto (abbreviated 4to or 4°) is a book or pamphlet produced from full 'blanksheets', each of which is printed with eight pages of text, four to a side, then folded twice to produce four leaves (that is, eight book pages). Each printed page now presents as one-fourth size of the full blanksheet.The earliest known European printed book is a quarto, the Sibyllenbuch, believed to have been printed by Gutenberg in 1452–53, before the Gutenberg Bible, surviving only as a fragment.