There was an expectant father who had spent all of his vacation time waiting for the offspring to arrive; he and the missuz were waiting- at his in-laws’ place. As he had no vacation left, he tells his father-in-law, “When my son comes, do not call up my office and say that I have become a father of a boy because I’ll have to shell out a lot for parties. Just leave me a message that the clock has arrived. This will be our code for the arrival of the baby.”
The offspring does finally arrive one day, but it’s a daughter. The father-in-law now thinks to himself, “If I tell him that the clock has not arrived, he’ll misunderstand and think that something has happened to the baby and come rushing over.” So the father-in-law left the following message:
“The clock has arrived, but the pendulum is missing.”