Parametric Coasters

Towards the bottom of the wikipedia article on Parametric Equations - https://en.wikipedia.org/wiki/Parametric_equation - there is a section entitled "Some sophisticated functions". The first two of these functions can be used to make coasters. Pictures of the functions are at - https://commons.wikimedia.org/wiki/File:Param_02.jpg - and at - https://commons.wikimedia.org/wiki/File:Param_03.jpg - The openSCAD code can be used to construct any of the pictured functions. Here are 9 coasters ba