《资治通鉴·后周纪·后周纪五》
臣下谨慎地按照古代的方法，用黑黍子粒来定出尺寸，长九寸、直径三分的作为黄钟律管，与当今黄钟的声音相互应合，以此推算，得出十二音律。
臣谨如古法，以秬黍定尺，长九寸径三分为黄钟之管，与今黄钟之声相应，因而推之，得十二律。
The minister cautiously followed the ancient methods, using black millet grains to determine the size, and used a nine-inch long and three-inch diameter as the Huangzhong pitch tube, which corresponds to the sound of Huangzhong today. Based on this, the twelve notes were deduced.