They are used to support a clean room photographic machine called a stepper. The machine imprints or exposes the patterns used for developing circuits on wafers in the making of micro-chips that are used in cell phones.
These two pedestals were replaced with two bigger ones that are each 3 times the size on the ones you see. Each of these that you see will support around 100,000 lbs and were built to a standard of about 1/1000 of an inch.