Ernst Mach was an Austrian physicist and philosopher and is the namesake for the "Mach number" (also known as Mach speed) and the optical illusion known as Mach bands.
An interesting read, although a bit dated wrt the discussion of the senses. I was reading this primarily to look for evidence of Mach's principle, and yes, I found a few statements unmentioned in wiki where Mach tries to assert a relativity of all Geometry... I guess it might not be referring to rotation, but it can easily be seen as a book that may have been planting the seeds in Einstein's head.