What is "to sweat coin"

Sweat \Sweat\, v. t.

1. To cause to excrete moisture from the skin; to cause to perspire; as, his physicians attempted to sweat him by most powerful sudorifics.

2. To emit or suffer to flow from the pores; to exude.

   It made her not a drop for sweat.
   --Chaucer.

   With exercise she sweat ill humors out.
   --Dryden.

3. To unite by heating, after the application of soldier.

4. To get something advantageous, as money, property, or labor from (any one), by exaction or oppression; as, to sweat a spendthrift; to sweat laborers. [Colloq.]

   To sweat coin, to remove a portion of a piece of coin, as by shaking it with others in a bag, so that the friction wears off a small quantity of the metal.

   The only use of it [money] which is interdicted is to put it in circulation again after having diminished its weight by ``sweating'', or otherwise, because the quantity of metal contains is no longer consistent with its impression.
   --R. Cobden.