c. 2670–2620 BC: The reign of the pharaoh Sneferu and his vizier Nefermaat. Sneferu leads a campaign in Nubia and returns with about 7,000 prisoners, who would be employed as servants in the royal estates. Sneferu then sends an expedition to Libya which brings back 11,000 prisoners and 13,100 heads of cattle.[2] Sneferu sends 40 ships to Byblos for the retrieval of cedar wood for the construction of ships.[10] Under Sneferu's reign and that of his son Khufu, copper mines and turquoise quarries are developed in Sinai. The tomb of Hetepheres I, wife of Sneferu and mother of Khufu, demonstrates that cabinetry and jewelry are well-developed.[11] A depiction of plowing painted in the tomb of Itet and Nefermaat in Meidum is the earliest testament to the technique in Africa.[12]