《梁书·列传·卷二十一》
所以圆形利于滚动方形益于搁置静止，是器物用处的不同；金刚强而水柔弱，是品性的差别。
故以圆行方止，器之异也；金刚水柔，性之别也。
Thus roundness facilitates rolling, and squareness benefits placement and stillness; they are different in the functions of tools; the diamond is firm and water is gentle, which are differences in qualities.