Lawn mower

«"Well, this is our lawn. But we consume it. Indirectly, of course - through our sheep. And the advantage is that it doesn't consume us. Have you ever pushed a lawn mower? The stupidest machine ever invented - for one of the stupidest of purposes. But I digress. We solved our problem with a portable electric fence which could be used to move our flock of sheep about the lawn like a gigantic mowing machine, but leaving most of it free at any time.»

Walden two, B. F. Skinner