ShakeBy: Eric Prum, Josh Williams An artisinal cocktail book by the entrepreneurs who invented the The Mason Shaker cocktail shaker, whose mission is to bring cocktail crafting out of the bar and into the home. Design, cocktail, and culinary enthusiasts Eric Prum and Josh Williams realized that while cocktail bars have sprouted up just about everywhere, good drinks still couldn't be found in the one place where they always mixed them: at home with friends.