Two glass balls

A Russian, a Chinese and a Czech are shipwrecked on an island of
cannibals. The medicine man comes to them and says: "We are cannibals,
I’ll only spare your life under one condition. I’ll lock you up in a hut
with two glass balls and if you show me something with the balls that I
haven’t seen yet, we won’t eat you."

In a week, the medicine man comes
to the hut to see the Russian. He’s sitting in the centre and the balls
are floating above his head. The medicine man says: "I’ve seen that, to
the pot!"He goes to the hut to see the Chinese, who’s sitting and the
glass balls are flying all around the hut. The medicine man says: "I’ve
seen that as well, to the pot!" He comes to the hut to see the Czech,
opens the door and says: "That I haven’t seen in my life yet, the
idiot’s lost one and broken the other!"