Frost opens chestnut burrs, ma'am, and it takes a good shake to bring them down. 路易莎·梅·奥尔科特.小妇人.
Formerly two horizontal disk-shaped stones or burrs were employed, the lower one stationary and the upper one revolving in a horizontal plane and crudely crushing the grain between them. Edward W. Byrn.十九世纪发明进展.