Old crushing system, which is still used in this days. The basic structure has not changed too much, but the start system has evolved with the times.
The millstone olearia is made of a circular stone with circular shape in which centre gets up an axis or vertical tree where other horizontal axis is fitted that holds one or two cylindrical millstones with a hole in the centre of them, made of stone (granite, basalt, etc.). When people moved this stone what produced was rotation and translation movement produced for the difference of length that existed between the interior and the exterior radius. The slipped of the stone on its base causes a decelerate action on the crushed olive.
Millstone olearia is known from the antiquity. With human traction
Source: Pieralisi España S.L