《宋书·志·卷十一》
阴阳协调则用圭表测曰影时表影长度就符合标准，律与节气相应就会使律管中的灰飞出。
夫阴阳和则景至，律气应则灰除。
If yin and yang are in harmony, use a sundial to check the length of the shadow of the gnomon. When the length of the shadow is in accordance with the standard, the pipe of the pitch will cause the ashes to fly out when the pipes of the pitch correspond to the solar terms.