What was the simplest physical instrument?

Question

What simplest experimental physical instrument
produced a result, which was actually recognized
by Nobel prize in physics.

Answer 1

My vote goes to Robert Millikan (1923 Nobel prize) and his oil-drop experiment by which he discovered and measured the quantum of charge. The instrument wasn't much more than a chamber into which he sprayed an oil mist (ref.). He got the oil drops charged by x-rays and applied a variable electric field to cancel the effect of gravity on the drops. When he measured the applied field he found it was always an integer multiple of one value, showing the charges were quantized.

Answer 2

The blackbody?

Wilhelm Wien 1911 Physics Nobel Prize.

Answer 3

A Cloud/Bubble chamber. It's basically just box of gas/liquid. A transistor's pretty simple too, but not that simple.

Answer 4

A level?