Manhattans and Measuring

I won a bottle of whiskey after a football game and decided to attempt to make one of my favorite cocktails, a Manhattan on the rocks. If you're unfamiliar with a Manhattan, it's simply booze mixed with less-strong booze. You take about 2.5 ounces of bourbon and add about 3/4 of an ounce of sweet vermouth. Then toss in a dash of bitters, shake with some ice and you're off to la-la land. The problem I had in making this cocktail was simple, I have no measuring devices that will tell me exactly one ounce. Everything is tablespoons, milliliters or cups. But I did have a cold recently, and I found the cup that comes with a bottle of Nyquil to be just about the perfect measuring device. Now I just hope I don't catch anything from my Manhattans.