1 sentence

1. 古人通过圭表投下的影子来确定冬至和夏至。

   gǔ​rén tōng​guò guī biǎo tóu​xià de yǐng​zi lái què​dìng Dōng​zhì hé Xià​zhì.

   The ancients determined the winter and summer solstices by observing the shadows cast by the gnomon.

   Source: Dong Chinese Dictionary