The torus (or doughnut) is the simplest object in Topology. But it also has interesting properties as a piece of solid geometry which has been studied by mathematicians for centuries
From a woodturning point of view it is not too difficult, though it requires a "jam chuck" or other holding device for finishing
As a plaything it has a very tactile feel about it and if it is on display people will be drawn to pick it up and play with it
A torus can be fairly thick and not very wide (like this one) or thin and large (like an inner tube)
In this case the outside diameter is 120mm and the thickness is 40mm. The hole in the middle is also 40mm. A later project shows how two toruses of this size and be linked through each other (should it be "tori" and not "toruses")