Olive oil was used for different purposes in the Temple, among them to mix into the meal-offerings and to light the Menorah. The Mishnah on today’s daf (=page) teaches that there were different levels of quality of the olive oil, and while the Menorah needed the purest oil (see Shemot 27:2), the menahot could use a second-level quality oil.
The Mishnah explains that there were three harvests of the olive crop: first the olives at the very top of the tree that ripen first, then the olives that are in the middle of the tree ripen, and finally the olives that are at the bottom ripen. Each harvest produces three levels of oil – the finest quality oil, where the olives are pounded in a mortar and simply left in a reed basket to drip; the second level oil, where they are pressed with a beam in an olive press, and the lowest quality oil, which is produced by grinding up what is left of the olives. Only the first collection of each harvest could be used in the Menorah; the others could be used in the meal-offerings.
The beam, or korah, of the olive press forces the oil out of the olives by means of pressure applied by a weight. The basket with the olives is placed on a raised spot and a strong, heavy beam is placed across it with one side placed in a wall and the other with a heavy stone. The oil then runs into a quarried hole in the ground or into storage utensils arranged for this purpose.
The lowest quality oil, which was produced by grinding up the olives, was done with the grindstones that were ordinarily used to process grain into flour. This was usually accomplished by means of a hand grinder, which involved two stones, the bottom one set in the ground and the upper one that turned on the bottom one. The material to be ground was placed in between these two stones. The top stone had an indentation where a pole could be placed to allow it to be turned by hand.