The 400-year-old, 34.98-carat Beau Sancy diamond, one of the world’s oldest with a royal provenance and currently in private hands, will be put on auction by Sotheby’s auction house in Geneva in May. Currently held at Sotheby’s in Paris, it is expected to fetch $4 million. The Beau Sancy is believed to have belonged to King Henry IV of France and Marie de Medicis.