《天工开物·上篇·粹精》
建造水碓的困难在于选择埋臼的地方，如果臼石设置的地势太低，就有可能被水淹没，臼石设在地势太高的地方，水就上不去。
盖水碓所愁者，埋臼之地卑则洪潦为患，高则承流不及。
The difficulty in building water mills lies in choosing a place to bury the mortar. If the mortar is placed too low, it may be submerged by water; if the mortar is placed too high, the water will not rise.