《明史·志·卷四十七》
郡县官年龄在五十岁以上的，虽然熟悉明达行政事务，而精力已衰，应该命令主管部门在民间选拔英俊突出年龄在二十五岁以上、资质禀性聪明敏悟、有学识才干的人征召到中书省，与年纪大的参互使用。
郡县官年五十以上者，虽练达政事，而精力既衰，宜令有司选民间俊秀年二十五以上、资性明敏、有学识才干者辟赴中书，与年老者参用之。
Prefects and county magistrates 50 years of age and over, despite their experience in administrative affairs, are declining in energy. As such, the relevant departments are ordered to recruit outstanding and intelligent individuals between the ages of 25 and 30 with knowledge and abilities to serve at the Secretariat, in alternation with the older officials.