《论衡·卷五·感虚篇》
这谷米不是气生成的。而必须有土才能长成，虽说天降谷是怪现象，但怪现象都源于同类事物。
今谷非气所生，须土以成。虽云怪变，怪变因类。
This rice grain is not generated by air. Instead, soil is required for it to grow. Although it is a strange phenomenon that grain falls from the sky, all strange phenomena have their origins in similar things.