Catholic Encyclopedia (1913)/Piatto Cardinalizio
An allowance granted by the pope to cardinals residing in curia or otherwise employed by the Church, to enable them to maintain their dignity with decorum. It was not given to cardinals supported in Rome by their sovereign, nor is it accepted by cardinals of noble family. The entire allowance was not always granted. If the cardinal had other revenues, he received enough to make up the amount of the allowance. This designation piatto was first used in the conclave of 1458. Paul II fixed the sum at 100 gold florins a month for cardinals whose revenues were not more than 4000 florins. This sum was called "the poor cardinal's plate". Leo XI intended to provide otherwise for the needful revenues. Paul V raised the piatto to 1500 scudi a year for cardinals whose ecclesiastical revenues were less than 6000 scudi. Then the custom was introduced of giving 6000 scudi annually to cardinals without ecclesiastical revenues. This sum was reduced in 1746 to 4000 scudi, as determined in 1464, and 1484, the amount allowed to-day, the cardinals renouncing their ecclesiastical benefices. For some distinguished cardinals the amount was larger. The piazzo cardinalizio is reckoned today at 4000 Roman scudi (about $4000). It is reduced according to the other revenues of the cardinal.
MORONI, Dizionario, LII, 274 sqq.