The hairshirt was a garment made out of animal hair. Generally, it would have a neck opening and rest upon the shoulders with the sides tied under the arms. There were numerous variations. Sometimes it was called a cilice or sackcloth. The idea was to wear something against the skin that would irritate it. For Catholics in the early days of Christianity, hairshirts were used as a method of repentance during the season of Lent, the 40 days before Easter. To intensify the irritation of the skin other items were added such as twigs, rocks, or metal.
During the Spanish Inquisition, the hairshirt was used after a voluntary or post-torture confession. If a person was suspected of heresy, they could either confess their sin or wait for the Inquisition Tribunal to charge them. The use of the hairshirt happened mainly in the New World viceroyalties.
The hairshirt represented the outward acceptance of the teachings of the Church. For people that faced the Tribunal, it was required that they publicly proclaim their devotion to God, Jesus, and the Church. It was an outward symbol that they had confessed their acts of heresy and would never be a heretic again. The Tribunal would sentence a person to wear a hairshirt for several hours in a public space such as a market or square.
Climates in the New World varied, but the heat and humidity seemed constant. The hairshirt was heavy by design. Wearers who were publicly embracing the Church would go without food and water for the duration of their sentence. Some people were sentenced to wear a hairshirt for seven days while others were sentenced to wear it for several hours while sitting in the hot sun of a public square.