What ratio of saltpeter, sulfur and charcoal needed to make black powder?

According to Dick's encycl. of practical recipes:





';Pulverize separately, 76 parts nitrate of potassa, 11 sulphur, 13 freshly burned charcoal, and mix tjem with a little water so as to form a cake when rolled onto a board.';





rx. 2140.





The key is to crush separately and I believe the ';parts'; means powder volume, but your milage may vary.What ratio of saltpeter, sulfur and charcoal needed to make black powder?
1/2/4