《汉书·志·地理志下》
从危星四度到斗星六度，称作析木的位置，是燕国的分星。
自危四度至斗六度，谓之析木之次，燕之分也。
From the fourth degree of the dangerous star to the sixth degree of the Big Dipper star is called the Ximu position, and is the dividing star of Yan.