  We prove that every bounded rational space curve of degree d and circularity
c can be drawn by a linkage with 9/2 d - 6c + 1 revolute joints. Our proof is
based on two ingredients. The first one is the factorization theory of motion
polynomials. The second one is the construction of a motion polynomial of
minimum degree with given orbit. Our proof also gives the explicity
construction of the linkage.
