The mentalist sends an email to a spectator and asks that he not open it until the end
The mentalist asks for the help of two spectators, on the table there are 28 pieces of a complete domino.
Spectators are invited to play a quick game of domino and they will let you know once they finish.
Once the game is over, the mentalist asks that they open the email that he sent to them at the beginning, this shows with total accuracy, the pieces with which the game begins and ends.