Via was designed in the late 1990s by the Japanese inventor Yasuo Aizawa, and for a while it was marketed (and possibly made?) by the Swiss firm Naef. Basically there are two sheets of clear perspex, with various bits cut out. They slot into two wooden base blocks, and because of the way the slots are cut in the blocks, the two perspex sheets are not parallel but rather they are further apart at one end than the other.
The device, once you have set it up on the table, allows marbles to roll down from the top to the bottom, but their motion is really remarkable. Initially you place a marble at the top, where the two sheets of perspex form rails supporting it. You place the marble at the end where the two sheets are closest together. The marble rolls in the direction where the sheets become wider apart, since as the sheets gradually separate, the marble starts to move downwards, so there is effectively a slight slope for the marble.
However the amazing part happens when the marble gets to the point where it can slip down bewteen the two sheets of perspex. Instead of noisily runing along the edge of the sheets, it now suddenly becomes silent, as it moves down bewteen the two sheets, still spinning as it goes. The marble follows a precise path between the sheets, until it falls clear, into another channel waiting for it below.
The marble now runs along the edges of this lower track, until they again widen sufficiently for the marble once more to fall between the two sheets, and continue on its silent spnning path. You can have several marbles all running simultaneously. Kinetic sculpture, beauty in motion, call it what you will. A beautiful toy that enchants everyone that sees it.