Making a versorium

In a block of polystyrene cut out a
rectangle parallepiped 2 X 2 X 4 cm.

Then cut into a pyramid.

Cut a household aluminium (aluminum)
foil, first in a rectangle of 1X4 cm.

Then give it a vane form and
drill it in the center with a pin.

Stick the whole on the top of the pyramid.

Your versorium is finished