Pounding the olives with stone mills is the method that dates back the farthest (figure 11). Weighing 16-28 quintals, two, four and even six granite millstones repeatedly mash the olives until a homogeneous paste with the right consistency is obtained.The millstones are shaped like cylinders or truncated cones. The surface of the travelling edges is uneven to avoid crushing the paste particle size so small as to hinder the subsequent separation of the liquid and the solid phases.