Sentence:  Each priest adorn'd was in a surplice white, / The bishops don'd their albes and copes of state, // Above their <WSD>rochets</WSD> button'd fair before, / And mitres on their heads like crowns they wore. 
Meaning of the word marked with <WSD> tags:  A white vestment, worn by a bishop, similar to a surplice but with narrower sleeves, extending either to below the knee (in the Catholic church) or to the hem of the cassock in the Anglican church.