[Caution: Do not perform this illusion if you suffer from Extreme Short-sightedness]
Step 1: Hold your left Thumb midway between the screen and your face so that just above the tip of your thumb you see the crazed smily.............
Step 2: Keep your thumb in that position. Now tilt your head 5 inches to your left (if you are left-handed). If you are right handed, then tilt 5 inches to your RIGHT so that this crazed smily

is just above your line of sight..........
Step 3: Now comes the tricky part SLOWLY move your thumb from current position towards your nose (whilst looking at it) until you can kind of see your one thumb become 2 blurry thumbs. For most folk this equates to an absolute minimum of about 8 centimetre (3 inch) distance from your nose.
Step 4: Now, your head should STILL have been tilted slightly. If it wasn't then those idiot folk will have to go back to step 2. Everybody else: Now tilt your head in the opposite direction and then back and close your eyes for about 5 seconds. When you open them, scroll down to be amazed!!!
HAHA, GOTCHA
The Only 'Astonishing' Thing About This 'Illusion' was the fact that you actually tried it.....

I hope someone was watching you do this at your house or office and they think you are insane.