《论衡·卷十一·说日篇》
北斗星在天下的正中，现在在人们的北面，天像个倾斜着的车盖，这已经很清楚了。
极其天下之中，今在人北，其若倚盖，明矣。 
Beidou is at the exact center of Heaven, and now is north of people. That heaven is like a slanted carriage cover is quite apparent.