1801 Schedule of Presswork Prices in E. Howe (1947) iii. 98 Twelves: Pot, such as ladies and christian ladies table part, 6mo. 35 Pica ems wide, 26 long.
1940 641/1 The pica em is a unit of measurement; it is equal to 1/ 6 in.
2002 P. Baines & A. Haslam iv. 75/2 One point measures slightly more than ½ inch with twelve points being known as a pica (or pica em).