41 BCE, the monopolies resumed until the end of Wang Mang's (r. 9–23 CE) regime. After his overthrow, the central government relinquished control of these industries to private businessmen. Liquor, another profitable commodity, was also nationalised by the government for a brief period between 98 and 81 BCE. After its return to private ownership, the government imposed heavy taxes on alcohol merchants. In addition to the state's short-lived monopolies, the government operated a separate sector of handicraft industries intended to supply the needs of the court and army, a practice that was continued throughout Chinese history, though the importance of this sector decreased after the Tang dynasty. Light industries such as textiles and pottery also developed substantially during this period. In particular, hand-made pottery was made in large quantities; its price dropped substantially, allowing it to replace the bronze vessels that had been used during the Zhou. Porcelain also emerged during this period. Han agriculture Widespread use of iron tools that had begun under the Warring States period allowed Chinese agriculture to increase its efficiency. These include the "two-teeth" plough and an early sickle. The use of cattle-pulled ploughs improved with the introduction of three-cattle plough which required two operators and the two-cattle plough requiring one. Another important invention was the invention of the horse collar harness, in contrast with the earlier throat harness. This innovation, along with the wheelbarrow, integrated the Chinese economy by drastically decreasing transportation costs and allowing long-distance trade. The seed drill was also developed during this period, allowing farmers to drill seeds in precise rows, instead of casting them out randomly. During the reign of Emperor Wu of Han, The 'Dai Tian Fa', an early form of crop rotation was introduced. Farmers divided their land into two portions, one of which would be planted, the other being left fallow. Han trade and currency Sources of revenue used to fund Emperor Wu's military campaigns and colonisation efforts included seizures of lands from nobles, the sale of offices and titles, increased commercial taxes, and the issuing of government minting of coins. The central government had previously attempted – and failed – to monopolise coin minting, taking power from the private commandery-level and kingdom-level mints. In 119 BCE the central government introduced the wushu (五銖) coin weighing 3.2 g (0.11 oz), and by 113 BCE this became the only legally accepted coin in the empire, the government having