"No two elements interlock, but all three do interlock" A three-component link with that property is called "Borromean" after the Borromeos, an Italian family from the Renaissance that used them as their family crest symbolizing the value of collaboration and unity.
B.Lindström and H.O.Zetterström [1]
proved that "Borromean
circles are impossible": three flat circles cannot construct them,
but by triangles they can. The Australian sculptor J.Robinson assembled three
flat hollow triangles to form a structure (called
P.Cromwel recognized it in a picture-stone from Gotland [2],
and it are exactly
these and other symmetrical combinations of three and four hollow triangles
that were considered by H.S.M.Coxeter [3].
In geometry, Borromean rings
appear as the regular octahedron {3,4} [4],
in Venn diagrams [5], in |