Compass and early explorers

In discussing explorers ( early) , we discussed and made a compass.  We took a needle and rubbed it in one direction for about 40 times.well rubbing it 20 times was not as good.  Also the first day, we put it on a thin plastic from a yogurt cup top.  This had its advantage as one could see the needle wobbling as it searched for the north direction.  Then our latest method has to be doing the same thing between two corks..