 The earliest extant copy of Cotrugli's manuscript "Libro de l'Arte de la Mercatura" ("Book on the Art of Trade") is kept in the National Library of Malta and is dated 1475, although the original manuscript was dated 1458.The text of his 1458 manuscript "Della mercatura e del mercante perfetto" is followed by an appendix containing an inventory and many journal entries.It contains an early description of the double-entry bookkeeping system, predating the description made by Luca Pacioli in his "Summa de arithmetica" of 1494.