《宋书·志·卷二十三》
前儒旧说，认为天地的形状就像乌蛋一样，天包在地的外面就像蛋壳裹住蛋黄相似，旋转不止，其形如浑然天成，所以叫做浑天。
前儒旧说，天地之体，状如鸟卵，天包地外，犹壳之裹黄也。周旋无端，其形浑浑然，故曰浑天也。
Ancient Confucian scholars and commentators said that the shape of heaven and earth is like a bird’s egg, heaven wraps around the outside of the earth like the eggshell wraps around the yolk, revolving without stopping, its shape as if naturally formed, so it is called the armillary sphere.