I once discovered that the fuel in my one litre collector tank, the fuel lines and carby are enough to start, warm up, taxi a km, takeoff and climb a couple of hundred feet.
Since then, instead of turning off tank taps, I habitually close taps near my knee after landing, so she runs out of fuel when I get to the hangar. Trying to avoid leaving mogas in the float bowl. Also makes it harder to start without checking fuel taps.