The round coin with a square hole in the middle, equivalent to half a tael, started a tradition carried through the Ching dynasty (1644-1911). The Emperor Wu of the Han dynasty (r. 157-187 B.C.) lowered the weight to.
「制錢」是秦始皇統一天下後所製定的，它是圓形方孔、重十二銖的「半兩錢」，「制錢」的傳統從此沿用到清末。