《淮南子·天文训》
这时太阳入息于虞渊水边，阳光余辉映照着蒙谷之畔。太阳每天行经九州、七舍，行程五亿万七千三百零九里，可将此分为早晨、白天、黄昏和夜晚四个阶段。
日入于虞渊之汜，曙于蒙谷之浦，行九州七舍，有五亿万七千三百九里，禹以为朝昼昏夜。
<translation>At that time the sun sank below the horizon at the waters of Yu-yuan, the sun’s afterglow covered the slopes of meng-gu. The sun travels five hundred seventy-three million nine hundred and nine miles every day in its path through the nine states and seven lodges. This path can be divided into four stages: morning, afternoon, dusk and nightfall.