One of my early jobs doing museum work involved going around and calibrating all the hygrothermographs in the galleries. These are the little seismic-activity-looking machines that you find in the corner of museum galleries, quietly scratching out any fluctuations in the carefully controlled climate. My boss at the time told me that the fluctuation readings are based on the reaction to human hair. Inside certain models of these machines is a little bundle of human hair stretched between two clamps. In trying to find more information about the use of human hair in hygrothermographs, I found a rather interesting letter about using a stolen lock of hair in one of these mysterious machines.