Triquetra
Three circles on the corners of an equilateral triangle, each passing through the other two centres, so every pair is a vesica. One strand, over and under. The Crelvo mark is drawn from exactly this construction.
In the faith
Christians read it today as the Trinity, three in one and one unbroken line. In the early Insular manuscripts it is ornament, and no writer of that age records what it meant; the Trinitarian reading is documented later.
Sources
- Euclid, Elements I.1