According to Tertullian, as quoted by Saint Jerome, in year 92, St John the Evangelist survived martyrdom at Rome under the Emperor Domitian by being immersed in a vat of boiling oil, from which he emerged unharmed. He was later exiled to island of Patmos. This event was traditionally said to have occurred at the Latin Gate, located on the southern portion of the Roman wall.
Trinidad trificela — The Three-Faced Trinity, an iconographic type of the Godhead that fell into disuse (or rather, was effectively outlawed as heterodox) in the wake of the Reformation. Also of note is the Scutum Fidei— the “shield of faith”, which proclaimed the Christian belief in the Holy Trinity: Three Persons, each distinct from each other, but sharing one divine essence.