In about 900 A.D. in northern Europe, potters' wheels began showing up with heavy round weights at their base. This picture is clearly much later, probably 19th century, but the wheels remain the same.

The potter kicks the wheel to keep it spinning at a relatively constant rate; this action is very similar to charging the filter capacitor in a power supply (for another example of stone wheels being used as capacitors, see Leonardo).

Note that the charging impedance can be controlled by kicking the wheel either barefoot (high impedance) or shod (low impedance).

The artist has made an error with the potter on the left: anyone who has used one of these wheels knows that you kick it with one foot at a time (the poor fellow would break his toes trying to work the wheel the way the artist has drawn him).

It has been pointed out that the actions shown here can also be thought of as charging an inductor; perhaps breaking toes can be thought of as insulation breakdown!