LOLSaints

Augustine's head, his head, his head is on fire.

In the Latin or Western Rite of the Roman Catholic Church, "first tonsure" was, in medieval times, the rite of inducting someone into the clergy and qualifying him for the civil benefits then enjoyed by clerics. Tonsure was a prerequisite for receiving the minor and major orders. Failing to maintain tonsure was the equivalent of attempting to abandon one's clerical state, and in the 1917 Code of Canon Law, any cleric in minor orders (or simply tonsured) who did not resume the tonsure within a month after being warned by his Ordinary, lost the clerical state. Over time, the appearance of tonsure varied, ending up for non-monastic clergy as generally consisting of a symbolic cutting of a few tufts of hair at first tonsure in the Sign of the Cross and in wearing a bare spot on the back of the head which varied according to the degree of orders. It was not supposed to be less than the size of a communicant's host, even for a tonsuratus, someone simply tonsured, and the approximate size for a priest's tonsure was the size of a priest's host. Countries that were not Catholic had exceptions to this rule, especially in the English-speaking world. In England and America, for example, the bare spot was dispensed with, likely because of the persecutions that could arise from being a part of the Catholic clergy, but the ceremonious cutting of the hair in the first clerical tonsure was always required. 

The fuller form of clerical tonsure led to the wearing of a skull cap in church to keep the head warm. This skull cap, called a zuchetto, is still worn by the Pope (in white), Cardinals (in red) and bishops (in purple) both during and outside of formal religious ceremonies. Priests may wear a simple black zuchetto, only outside of religious services, though this is almost never seen except as a practical garment used for warmth by some monks. Some priests who held special titles (certain ranks of monsignori and some canons, for instance) formerly wore black zuchettos with red or purple piping, but this too has fallen out of use except in a few, extremely rare cases.