Rubber Bearing Pad
Mason Industries - BBNR4X4 - Natural Rubber Load Bearing Pad - 4"L x 4"W x 1"H
Each pad can handle 2400 pounds. Deflection at max load is 1/8".
http://www.penntoolco.com/mason-rubber-vibration-isolation-load-bearing-pads/
https://www.mscdirect.com/product/details/86434842