This is actually a real problem with semiconductors. I often need carefully matched sets of transistors and diodes, and a quick and easy way to get them "good enough" is just to measure either a diode or the B-E junction of the transistor with a multimeter in "diode check" mode. I pin the paper strip to a piece of wood and let the temperature stabilise for about half an hour before I start, and only touch the component with the meter probes.

You can try this yourself. With any given 1N4148 you'll see the Vf indication on the meter change as the microscopic current warms the junction up a tiny bit. If the room (and thus the diode) is fairly cold, it can detect the heat from your finger at about 1cm away.