The performer borrows a hat and a fairly thick handkerchief from the audience. He shakes the hanky to prove that it's empty. Then he crumples it up and discovers an egg in it, which he drops into the hat. This procedure he repeats until the hat must be full of eggs, but when he turns it over and shakes it none appear! He returns the hat and the hanky to the audience.
The trick is quite simple: the egg is attached to an invisible thread which has a tiny hook at the other end. When the performer first crumples the hanky up, he must attach the hook to the top of it; the egg and thread will of course have been palmed beforehand. When it is time to turn the hat, the thread can be detached and it and the egg palmed and placed aside.
The egg must be blown out — so as to prevent accidents! Or, better, it's made of porcelain. In any case, it must be very light. If other egg tricks are being done, it can be included in the basket (see "cake in a hat" — method 2).
When the performer spreads out and shakes the handkerchief to demonstrate that there's nothing there, the egg is of course suspended from it as shown. Thus there must be no backlighting to reveal it. The performer must contrive to bend the top of the hanky back an inch or more so that the egg doesn't touch it during the shaking. It must be light so as not to cause a crimp or other revealing fold in the handkerchief.