One of our old (now in his thirties) undergraduate students was given
an Euler's disk toy for Christmas a couple of years ago. He brought to
our house soon after receiving it to show it off. It is truly
remarkable to watch, though the physics is mundane. The difference in
this toy was scale!
The disk is large and massive. In retrospect (dangerous) I will
estimate it had a diameter between 15 and 20 cm and a mass approaching
1 kg. The edges of the disk were accurately machined and polished, and
the disk appeared to be highly symmetrical. It spun like a spinning,
falling coin on a horizontal concave second-surface-mirrored glass
base, also of considerable mass. The result was somehow eerie, and the
motion itself was somehow ponderous, accompanied by a rather loud,
continuous drone, which judging by the duration of the motion must
have been an appreciable product of the initial kinetic energy of the
system. The toy must be used on a solid support, of course.
It was obvious to me at the time that the toy could be made into
something even more marvelous by driving its support with concealed
tip-tilt actuators. The motion could appear to be perpetual, like the
motion of one of my all-time favorite toys, Top Mystery.
While the toy was really quite impressive, when I found out how much
is sold for I decided not to buy one for myself. I don't even own a
Levitron, for the same reason, though I saw my first one at Hamley's
in London in 1994. I even considered constructing my own at that time.
It is only now getting down into the price range I think I can afford,
and performing better, and becoming much easier to start.