I guess cash has plenty of fiber in it.
http://www.newsobserver.com/news/story/1447519.html
One of our kids swallowed a couple of coins as a toddler. The doctor reassured us that the denominations in question were small enough that they would pass right through. We decided to take his word for it rather than check.
For $400? Yeah, I'd be willing to do a little mining.
I'm going to refer to this story when I got to the bank to make a car payment and they try and refuse a big 'ol pile of dog crap as payment.