For the student looking to put together a classic science fair project from the past, this hygrometer from the April 1944 issue of Popular Science should fit the bill.  A hygrometer is simply a device to measure humidity, and this one uses a single human hair as the sensor, just like the first one constructed by Horace Bénédict de Saussur in 1783.

Construction will require a bit of trial and error, but is quite simple.  First, a strand of hair about four inches long is washed “in cleaning fluid.” Another set of plans available on the internet recommend the use of dilluted rubbing alcohol, which should probably work as the cleaning fluid. The idea is to remove the oil from the hair to make it more sensitive to changes in humidity.

One end of the hair is attached to a fixed point, and the other end is wound around a large-eyed sewing needle. The 1944 article recommends attaching it to the needle with sealing wax.  However, you should be able to use other fancy stuff, such as hot glue or possibly just regular glue.

The needle is held in place by bearings consisting of shirt buttons. Finally, a pointer is attached to the needle. As the humidity changes, the hair expands and contracts, which causes the needle to rotate. The amount of rotation is visible on the pointer.