November - Les Tres Riches Heures du duc de Berry, c. 1415. I remember being fascinated by these illustrations when I first discovered them as a child. A treasure trove of historical tidbits. And to find out how they made all the colors is absolutely enthralling. Most information on this board thanks to Jean Longnon & Raymond Cazelles (when I googled this book title & lapis lazuli on the internet), as well as Wikipedia.