Frost's cube of nine, Whipple Museum of the History of Science, Cambridge. Length 289mm; breadth 286mm; height 270mm. Turned square ebony base carries glass cube (edges covered with gold paper) which contains 7 glass plates. Each plate, together with the back and front of the cube carries 81 numbers, printed on paper, arranged in 9 rows of 9 columns. Each position on the grid has two numbers, one facing in each direction. These numbers run from 1 to 729.