"Therefore, one does not know the height of the sky unless he climbs a high mountain; one does not know the thickness of the earth unless he stands by a deep ravine; one does not know the greatness of learning unless he hears the teachings of the ancient kings."

故不登高山，不知天之高也；不临深溪，不知地之厚也；不闻先王之遗言，不知学问之大也。

~ Xunzi (荀子, c. 313–238 BCE), from "Xunzi, Encouraging Learning" (《荀子·劝学》)