《周礼·冬官考工记·磬氏&车人》
把兵矢、田矢的长度分为五等分，二等分在前，三等分在后，则前后重量相等。
兵矢、田矢，五分二在前，三在后。
Divide the length of the battle arrow and hunting arrow into five equal parts, with two parts in front and three parts at the back, so that the weight distribution was equal.