How grandma lost her eyesight.
(Click to enlarge)
There are no spirals in the center of this 80 x 82 inch quilt, only straight lines.
From the exhibit "Infinite Variety: Three Centuries of Red and White Quilts" at The American Folk Art Museum in New York. The artist is unknown, but the quilt was thought to have been made between 1890-1910.
New Scientist featured this design in one of their "Friday Illusion" posts.
– Friday Illusion: 100-year-old quilt reveals 3D vortex, New Scientist>>
– American Folk Art Museum>>