Experiment showing that light is not travelling in straight paths.
In Riedern A.S. in Klettgau on May 24 2001 between 11 and 12am, the engineer Wilhelm Martin (deceased since 2009) conducted on experiment (which was witnessed by Rolf Keppler) with a theodolite (leveling device) called a dumpy level.
Source:
http://www.rolf-keppler.de/lichtkrumm.htm