Literature Reference: 碓上米不舂，窗中丝罢络。看渠驾去车，定是无四角。—— 《读曲歌五首 二》 Unhulled rice on the millstone, silk threads spun by the window. Watch him drive away, surely a squareless wheel. Source from 'Du Qu Ge Wu Shou Er'.
无: No, it's clean, won't happen.
角: Surname, forehead bone, measure word.
Meaning: Lacking corners symbolizes harmony, smoothness, and avoiding conflict.