《汉书·传·何武王嘉师丹传》
正好有人上书说古代用龟贝做货币，现在用铜钱替换它，百姓因此贫穷，应该更改货币。
会有上书言古者以龟贝为货，今以钱易之，民以故贫，宜可改币。
It just so happened that someone submitted a memorial saying that in antiquity, tortoise shells and cowries were used as currency, but now they have been replaced by bronze coins, so the people have grown poor, and the currency should be changed.