As for length, the theory defined the diameter of a grain of black millet as 1 bu (分; 0.3 centimeters or 0.1 sun), while the length of an ancient flute called Kosho, a standard instrument to fix the chromatic scale, as 90 bu (9 sun [a unit of length]).
長さは秬黍（きょしょ。クロキビ）の1粒の幅を1分（0.1寸）、黄鍾と呼ばれる音律を出す笛の管の長さを90分（9寸）とした。