This is one embodiment of the AMAZING GEOMETRY MACHINE
as a build it kit using special SPACE CHIPS with offset holes, 3/8″ diam x 10 in clear acrylic tube, and colored 2mm elastic chord. Three separate colored loops (red, yellow,blue) trace the edges of two intersecting tetrahedra. Each color passes through each tube exactly once.
Original paper published:
Forma, Vol. 15 (No. 2), pp. 149-155, 2000 SciPress PDF