Watermelon, eaten in time

(Surrealist joke)
In one city lived a man, famous for his wisdom, venerable age, but very poor. One day the king heard about the wisdom of the elders and told him that he wished to visit him at his house and listen to his words.
— What are we going to treat the king? — asked his wife. — We have almost nothing!
— Bring what you have, and do as I tell you, — replied the elder.
When the king came, the wife of the old man brought a watermelon. The owner took the watermelon in his hand, felt his fingers and said to his wife:
— Is watermelon better than this. Go and get it.
Wife took the watermelon, then came back, and in her hands was again a watermelon. The old man and his felt and told her to take this and bring another. The wife said nothing and immediately did as he said. This time, the husband was satisfied. He cut up the watermelon and gave it to the king a treat. After a conversation with the elder king returned to his Palace happy and satisfied by the hospitality shown by the old man. He did not know that the house of the old man only had one watermelon...