The *technology of Greek *agriculture was simple, and apparently underwent little development. Breaking up the ground, which was fundamental to sowing, weed-control, and preservation of moisture, was achieved by simple symmetrical ploughs, which did not turn the soil, or by mattock and hoe. Ploughs and mattocks occasionally appear on vases and the (all wood) plough is described at length in Hesiod (Op. 427 ff.). Cereals were reaped with a curved sickle, and vines and olives pruned with an implement which is scarcely distinguishable.The processing of crops required more sophisticated equipment. Threshing cereals required a stone floor on which the grain was threshed by animal hoofs or perhaps animal-drawn sledges, the runners of which may have been toughened by the addition of obsidian flakes; winnowing was by basket and shovel. Pressing grapes could be done by human feet in a basket, vat, or stone press-bed, but olives had to be crushed (see olive).