This is a view of the glass blank for the mirror to the Hale telescope. It weighs tons and they have it on display at the Corning Museum of Glass in Corning New York. This one is here because it has some tiny blemish or fault. Another was cast and polished to a mirror like shine and sent out west via train. While the second mirror was slowly cooling and annealing, Corning experienced a flood of its river which went right up to the Corning factory and threatened to ruin the new massive glass, but with heroic efforts they kept the water at bay and it was successful.