Hello Alexander. I happened on your site and worked my way to the webpage about the twin brothers. As I scrolled down the page I began to get a feeling of Deja vu. The "puzzles" that the people reword and present are identical to a scene from the movie Labyrinth made in 1986 when the "heroine" had to decide which door led to the castle and which one led to certain death. The sentinels guarding each door made it known that one of them tells the truth and that the other lies. Essentially they play out a scene of those very puzzles. I just thought it might be a nice anecdote that you might interested in.

Dear Amber:

Thank you for a reminder. I forgot about the movie.

However, the puzzles were known long before the idea of that movie has cropped up in somebody's mind. It would be nice to trace their origin. I won't be surprised if they originated some time in the 19th century.

Thank you again,
Alexander Bogomolny