The upside-down grain measure knob  is named for the “dou,” an ancient unit for measuring grain. One author calls this a “covered container knob” while others translate it as an “inverted dou” or “overturned dou” knob. Up to the Han dynasty these were only used for jade seals. This knob was probably a result of the difficulty involved in cutting jade, a very hard stone, into anything other than a simple shape.

• Pinyin: fù dŏu niŭ