What about corn cobs?
http://boards.straightdope.com/sdmb/archive/index.php/t-130601.html
Here’s one crucial - I said CRUCIAL! - tip.
You have to keep the cobs to be used in a bucket of water. You don’t even want to find out what happens with a dry one.
Be warned!
What about corn cobs?
Two red cobs to do the job. One white cob to check.