《论衡·卷十一·说日篇》
要是太阳和月亮合在一起相当于两块玉璧重迭，就是日全食了。
其合相当如袭者，日既是也。 
If the sun and the moon were combined together and were the equivalent of two jade discs lying one over the other, then that would be a total solar eclipse.