The beautiful princess
On a magical island, there lived 3 men: the poor knight, the rich knight, and a wanna-be knight. Then, there is this random supposedly-beautiful princess who wanted to marry the poor knight for some reason (don't ask me). Now, consider these 3 facts:
The poor knight only tells the truth
The rich knight only tells the truth
The wanna-be knight only tells lies
And now here is the problem: She has no way of telling the differences between the 3 knights. What should poor knight say in order to prove that he is the poor knight?