At Wadi Maghareh in the Sinai a rock inscription depicts Khufu with the double crown. Khufu sent several expeditions in an attempt to find turquoise and copper mines. Like other kings, such as Sekhemkhet, Sneferu and Sahure, who are also depicted in impressive reliefs there, he was looking for those two precious materials. Khufu also entertained contacts with Byblos. He sent several expeditions to Byblos in an attempt to trade copper tools and weapons for precious Lebanon cedar wood. This kind of wood was essential for building large and stable funerary boats and indeed the boats discovered at the Great Pyramid were made of it.