In Medieval Europe, manuscripts and formulas on the preparation of colors and dyes used by chemists and artists contained many references to natural plant extracts, The yellow stigmas of aromatic saffron (Crocus sativus) were crushed and used both as a medicine and colorant as far back as the ninth century BCE. In 1437 CE, a manual was written by Cennini, II Libro del Arte, a collection of recipes on the preparation of tempera and block-printing inks from saffron and brazilwood (Caesalpinia echinata), Finely divided brazil wood was prepared by scraping sticks with a knife.