The young clerk's responsibilities included bringing the judge a hot cup of coffee at the start of every day. Each morning the judge was enraged that the coffee cup arrived two-thirds full. The clerk explained that he had to rush to get the coffee delivered while it was still hot, which caused him to spill much of it along the way.
None of the judge's yelling and insults produced a full cup of coffee, until he finally threatened to cut the clerk's pay by one-third if he continued to produce one-third less than the judge wanted. The next morning he was greeted with a cup of coffee that was full to the brim, and the next morning and the morning after that.
The judge couldn't resist gloating over his success and smugly complimented the clerk on his new technique. "Oh, there's not much to it," admitted the clerk happily, "I take some coffee in my mouth right outside the coffee room, and spit it back in when I get outside your office."