《北史·列传·卷三十八》
 钱币的出现，本来是用它作媒介使交换双方互通有无，方便交易。所以，钱币分量的轻重，各个朝代都不相同。
盖钱货之立，本以通有无，便交易，故钱之轻重，世代不同。
The creation of currency was originally intended as a medium for the exchange of goods between two parties to facilitate trade. Therefore, the weight of the currency varied in different dynasties.