You are supplied with a die, a small tube with a lid, and a large tube with a lid.
Keep the large tube and lid in your pocket.
Give the spectator the small tube, cap, and die with instructions to place the die in the tube and remember the number that is on top, then turn around. Have them replace the lid on the tube so that you cannot see the die. After that is done, turn back around and give him the large tube and lid and ask him to examine it to see that there is nothing tricky about it.
Now, while he is examining the large tube, you pick up the small tube and turn it upside down and hold it in the position that is illustrated (you will find that when the die lies flat against the lid, you can see the number that is on top through the lid of the tube).
Don’t sneak a look at it, look right at it just like you would if there were nothing wrong with it. Now give the small tube to the spectator and tell him to place the small tube inside the large tube and seal it with the lid. Now tell him that you do not want to touch the tube, so you want him to hold it against your forehead. When he does so, you concentrate for a moment and name the number on top.