《明史·志·卷五十六》
户部尚书郭敦说： 以粮换盐的条令规则已经减轻，而商人前来换盐的很少，请求以十分作为标准，六分支付给输送米到京城粮仓的人，四分支付给辽东、永平、山海、甘肃、大同、宣府、万全已输送米的人。
户部尚书郭敦言： 中盐则例已减，而商来者少，请以十分为率，六分支与纳米京仓者，四分支与辽东、永平、山海、甘肃、大同、宣府、万全已纳米者。
Minister of Revenue Guo Dun said: The rules for exchanging grain for salt had already been relaxed, but few merchants came to exchange for salt, and he requested to establish ten fen as the standard, with six fen paid to people who had transported rice to the granary in the capital, and four fen paid to people who had already transported rice to Liaodong, Yongping, Shanhai, Gansu, Datong, Xuanfu, and Wanquan.