《汉书·志·刑法志》
天子的王畿有千里见方，总共有一百万井，规定缴兵赋的六十四万井，兵马四万匹，兵车万辆，所以称为万乘之主。
天子畿方千里，提封百万井，定出赋六十四万井，戎马四万匹，兵车万乘，故称万乘之主。
The imperial court of the emperor covers an area of one thousand li, with a total of one million wells, a quota of six hundred and forty thousand wells for military service, forty thousand military horses, and ten thousand chariots, hence the title of Wan Cheng (萬乘之主).