Emulating an earlier Franciscan missionary and saint, Francisco Solano, Serra made a habit of punishing himself physically, to purify his spirit. He wore a sackcloth spiked with bristles, or a coat interwoven with broken pieces of wire, under his gray friar's outer garment. In his austere cell, Serra kept a chain of sharp pointed iron links hanging on the wall beside his bed, to whip himself at night when sinful thoughts ran through his mind. His nightly self-flagellations at the college of San Fernando caught the ears of some of his fellow friars. In his letters to his Franciscan companions, Serra often referred to himself as a "sinner" and a "most unworthy priest."