Norse religion, focusing on Thor and Odin, the gods of war and death. The Viking warrior is often associated with violent fits of rage and frenzied fighting in modern popular culture, as reflected in meanings attached to the words berserkergang and berserker that would not have been the meanings understood by medieval Norse society. Such a fighting style may have been deployed intentionally by shock troops, and it has been proposed that the berserk-state may have been induced by consuming large amounts of alcohol, or through ingestion of materials with psychoactive properties, such as the solanaceous plant Hyoscyamus niger, as speculated by Karsten Fatur or by consumption of the hallucinogenic mushroom Amanita muscaria, as first hypothesized by the Swedish theologian Samuel Ødman in 1784 and later by the botanist F.C. Schübeler in 1885. The Norwegian battlfield archaeologist Are Skarstein Kolberg asserts that "...Ödman's hypothesis is not supported by the saga literature or by the archaeological record", and according to Roderick Dale, there is no evidence for it from the Viking Age or from Old Norse literature. Trade The Vikings established and engaged in extensive trading networks throughout the known world and had a profound influence on the economic development of Europe and Scandinavia. Other than in such trading centres as Ribe Hedeby in Denmark, Scandinavia was unfamiliar with the use of coinage, therefore its economy was based on bullion, that is, the purity and weight of precious metals used in exchange. Silver was the precious metal most commonly used, although gold was also used. Traders carried small portable scales, enabling them to measure weight precisely, which allowed an accurate medium of exchange, even lacking a regular coinage. Goods Organized trade covered everything from ordinary items in bulk to exotic luxury products. The Viking ship designs, like that of the knarr, were an important factor in their success as merchants. Imported goods from other cultures included: Spices were obtained from Chinese and Persian traders, who met with the Viking traders in Russia. Vikings used homegrown spices and herbs like caraway, thyme, horseradish and mustard, but imported cinnamon. Glass was much prized by the Norse. The imported glass was often made into beads for decoration and these have been found in the thousands. Åhus in Scania and the old market town of Ribe were major centres of glass bead production. Silk was a very important commodity obtained from Byzantium (modern day Istanbul)