These bottles are sold commercially for said purpose. It is very hard to find the hidden substance. I have caught kids with these things, kind of an optical illusion. You can buy the bottles from head shops, Im sure he did not construct it himself. The interesting thing is that I know what the bottles look like now, so you cant see the hidden cmpt., but the make of the bottle is obvious.

I just cant believe he was stupid enough to bring it on a plane as others have stated. These guys dont find their jobs due to brains.