&amp;#8220;The design relies on the simple principle of &ldquo;what you see is what you  get&rdquo; &mdash; the faucet fills the attached glass tube with exactly one liter  of water for washing hands, and it needs to be turned off again before  it will recharge. The brainchild of designers Yonggu Do, Dohyung Kim and Sewon Oh, the faucet is a clever bit of stingy design.&amp;#8221;
(via Elegant 1 ℓimit Faucet Cuts Water Use to a Single Liter | Inhabitat - Green Design Will Save the World)
This is brilliant. One of the biggest problems with reducing waste is that we have little idea how much we&amp;#8217;re using. This faucet removes all doubt. I wonder, though, if this allows the full 20 second recommended handwashing.