The following is from the July, 1979 Scientific American, article titled The Amateur Scientist: How to build a simple seismograph to record earthquake waves at home, by Jearl Walker
The construction of the Lehman Seismograph was described several years ago by Walker (1979), and its utility was discussed by Barker (1983). The seismograph can be rather easily built for $120 worth of ordinary lumber, hardware, plumbing and electronic parts, plus a necessary strip-chart recorder. The seismograph seems to have received little attention from geology and earth-science teachers and it appears that perhaps less than a dozen are in operation in the United States (G. Barker, personal communication). In spite of its simplicity, the Lehman seismograph is capable of recording earthquakes of Richter magnitude 5 which occur in the continental United States, and magnitude 6 elsewhere. It is sensitive enough to detect the tilt of a concrete basement floor as a person approaches or withdraws from it.