I love a good puzzle.
Some of my favorite kinds are strictly conceptual, meaning that once created, these objects require you to simply look and think about them. You can hold them, shake them, examine them . . . but you can't physically disassemble the completed object.
I have several such items at my house that just sit on a shelf and cause visitors to scratch their heads and say ". . . wait . . . how did you . . ?"
In this instructable, I'm showing how I put two standard tennis balls into a completely unaltered bottle.
For any readers that enjoy puzzles and are up for a challenge: stop reading, examine the photo above, and try to duplicate it on your own. To you brave souls, I bid you good luck and happy problem-solving; come back when you've got it and let me know how it went!
For everyone else, read on to see how I did this.
The bottle I'm using is a carafe I got at a local thrift store for 50 cents. The narrowest internal part of the neck is about 1 5/8" (4.1 cm) in diameter.
The balls are standard tennis balls and are about 2 5/8" (6.6 cm) in diameter.