File:Circular-cross-decorative-knot-12crossings.png

From CC-BY-SA licensed image by Wikimedia Commons user Takahe (see http://commons.wikimedia.org/wiki/File:4-Elemente-Eigenschaften.jpg and in particular http://upload.wikimedia.org/wikipedia/commons/archive/5/55/20091107085148%214-Elemente-Eigenschaften.jpg ).

A more exactly symmetrical version of this can be generated from the following self-authored public domain Vector PostScript source code:

%!
306 396 translate 1.1 -1.1 scale 38.75 setlinewidth/X{972 sqrt
10 add 3 sqrt mul 118 add}def/W{30000 sqrt 10 sub}def/Z{X 72
sub}def X neg 0 36 180 300 arc 0 W neg 200 120 60 arcn
X 0 36 240 0 arc 0 0 X 36 add 0 90 arc
0 X 36 90 210 arc W neg 0 200 30 330 arcn
0 X neg 36 150 270 arc 0 0 X 36 add 270 360 arc
X 0 36 0 120 arc 0 W 200 300 240 arcn
X neg 0 36 60 180 arc 0 0 X 36 add 180 270 arc
0 X neg 36 270 30 arc W 0 200 210 150 arcn
0 X 36 -30 90 arc 0 0 X 36 add 90 180 arc closepath
gsave 50 setlinewidth 1 .9 1 setrgbcolor stroke grestore stroke
4{50 setlinewidth 1 .9 1 setrgbcolor
0 W neg 200 91 109 arc stroke 
X 0 36 85 0 arcn 0 0 X 36 add 360 343.5 arcn stroke 
0 W 200 247 240 arcn -50 dup 3 sqrt div neg rlineto stroke 
38.75 setlinewidth 0 setgray 0 W neg 200 90 110 arc stroke 
X 0 36 86 0 arcn 0 0 X 36 add 360 342.5 arcn stroke
0 W 200 248 240 arcn -52 dup 3 sqrt div neg rlineto stroke 
90 rotate}repeat showpage
%EOF