《智囊(选录)·明智部·杨一清》
明朝时杨文襄奏请朝廷，重新设置专职交易马匹的官吏，严禁私自交易，把茶叶的利润完全收归官府所有，并通报到各番邦。
杨文襄乃请重行太仆宛马之官，而严私通禁，尽笼茶利于宫，以报致诸番。
During the Ming dynasty, Yang Wenxiang petitioned the government to reinstate officials dedicated to trading horses, and strictly forbade private trading. All profits from the tea trade were to be paid into government coffers, and the rules were publicised to all the foreign tribes.