《史记·八书·历书》
月朔大余十八日，小余八百四十九分；冬至大余三十六日，无小余；
大馀十八，小馀八百四十九；大馀三十六，无小馀；
On the 18th day after a new moon, its diameter is 18 minutes longer than its diameter on the day of the new moon. On the 849th day after a new moon, its diameter is 8 minutes shorter than its diameter on the day of the new moon; on the 36th day after a winter solstice, its diameter is 36 minutes longer than its diameter on the day of the winter solstice. It does not have a smaller diameter.