Image of Griffis-Duffy platform made by Charles W. Wampler and Douglas N. Arnold using Matlab. Click for high resolution image.

A Griffis-Duffy Type I platform consists of two equilateral triangles
with moveable legs connecting the vertices of one with the edge
midpoints of the other. With the base triangle in fixed position and
the leg lengths fixed but angles free, a point attached to the other
triangle traces out an algebraic curve of degree 40 in Euclidean
3-space. For more information, see A. Sommese, J. Verschelde, and C.
Wampler, "Advances in Polynomial Continuation for Solving Problems in
Kinematics," ASME J. Mechanical Design, 126:2:262-268, 2004, and
the book *The Numerical Solution
of Systems of Polynomials Arising in Engineering and Science* by
Andrew J. Sommese and Charles W. Wampler, World Scientific, 2005.