Dear of troy: it is not just the voltage rating of a capacitor that matters. More importantly, the area that is charged determines the amount of energy that can be stored. This is measured in "farads", eponymic for Faraday, I suppose. Some of the early experimentors used Leyden jars, which were coated on the inside with silver plating, I think. Several of them in series could give an extremely unpleasant surprise if discharged from one hand to the other. Interesingly, there are eels that can store up a charge powerful enough to cause careless wader in tropics to be stunned and drowned. The muscles act like a long string of Leyden jars, and store enough electrons to cause an appreciable current. I think I have read of it being possible to make a light bulb flash with their discharge. I'll try to see if I can find anything on Internet.