Thus the following solution that I give to our puzzle involves the pointed "oval," known among architects as the "vesica piscis."
"Amusements in Mathematics"
Henry Ernest Dudeney
Others say that the Crusaders introduced it on their return from the East, or that it was suggested by the Norman vaulting, or from the form of the vesica piscis, the most ancient of Christian symbols.
"English Villages"
P. H. Ditchfield
There are two openings of this cave; the one, the larger, is like a cage of railings, with the gleam of an altar in the gloom beyond, a hundred burning candles, and sheaves and stacks of crutches clinging to the broken roofs of rock; the other, and smaller, and that farther from us, is an opening in the cliff, shaped somewhat like a vesica.
"Lourdes"
Robert Hugh Benson