The Sumerians were compelled to establish one of the oldest land-and-sea commerce networks since their native country was mostly bereft of lumber, stone, and minerals. The island of Dilmun, which controlled the whole copper trade, may have been their most significant trading partner, but its merchants also made months-long excursions to Lebanon and Anatolia to obtain cedar wood and the Indus Valley to find gold and precious stones. Lapis lazuli, a blue valuable stone used in jewelry and artwork, was a favorite of the Sumerians, and there is evidence that suggests they may have traveled as far as Afghanistan to obtain it. In order to record their trade transactions, merchants employed cuneiform tablets to document these transactions.