The triple spiral was possibly the precursor to the later triskele design found in the manuscripts.
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Related symbols in classical Western architecture include the cross, the three-legged triskele or triskelion and the rounded lauburu.
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For instance, beside the figure of Odin on his horse shown on several memorial stones there is a kind of knot depicted, called the valknut, related to the triskele.
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More examples
Triskelion: a figure consisting of three stylized human arms or legs (or three bent lines) radiating from a center
A triskelion or triskele is a motif consisting of three interlocked spirals, or three bent human legs, or any similar symbol with three protrusions and a threefold rotational symmetry. ...
A symbol consisting of three (or sometimes more) connected curves or spirals
(triskeles) three legs or a three-legged design in a pinwheel shape.
This is a triple spiral related to the triquetra and relates to the sun, the afterlife, and reincarnation. It represents pregnancy and the movement of time, shown in a continuous line.