Borromean rings
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In mathematics, the Borromean rings are three simple closed curves in three-dimensional space that are topologically linked and cannot be separated from each other, but that break apart into two unkno
A monkey's fist knot
Regular octahedron
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In geometry, a regular octahedron is an eight-sided polyhedron with equilateral triangles as its faces. Known for its highly symmetrical form, the regular octahedron is a Platonic solid, and more gene
Sketch of a regular octahedron by Johannes Kepler
Kepler's Platonic solid model of the Solar System
Fluorite with octahedral structure
Two identically formed Rubik's Snakes can approximate an octahedron.