I still like the late astronomer Carl Sagan’s hypothesis in his book “Comet”. That through atmospheric/optical effects the gleaming core of a comet can sometimes take on distinct shapes and that sometime in the eleventh century a comet passed by earth that had a twinkling swastika-like center, seen by all humanity for a few nights.
The swastika pops up spontaneously, simultaneously, in art all around the world at this time—from Australian rock carvings to the Norman Bayeux tapestry.
The swastika quilt above dates from 1860-1880. The owner states that the quilt is hand-quilted at 9 stitches per inch.