With the exception of the introductory quotation from the Encyclopaedia Britannica, the following references are translations from authentic Portuguese works carefully preserved in the libraries of Portugal. They indicate how difficult it was to substitute pouring and sprinkling in place of immersion as the accepted mode of this ordinance of the Christian church.
Baptisteries belong to a period of the church when great numbers of adult catechumens were baptized, and when immersion was the rule. We find little or no trace of them before Constantine made Christianity the state religion; i.e. before the 4th century; and as early as the 6th century the baptismal font was built in the porch of the church and then in the church itself. After the 9th century few baptisteries were built, the most noteworthy of later date being those at Pisa, Florence, Padua, Lucca, and Parma. . . . Some baptisteries were divided into two parts to separate the sexes; sometimes the church had two baptisteries, one for each sex. A fireplace was often provided to warm the neophytes after immersion. . . . As soon as Christianity made such progress that baptism became the rule, and as soon as immersion gave place to sprinkling, the ancient baptisteries were no longer necessary. . . . In England, a detached baptistery is known to have been associated with the cathedral of Canterbury.—Encyclopaedia Britannica (11th ed.), art. "Baptistery," p. 370.
"In the beginning of Christianity the ceremony of baptism was performed by immersion. In those early days the right was granted only to those of mature age and after being well proven in discipleship. The teachers were called catechists. According to Catholic doctrine there is but one baptism."—Novo Diccionario Encyclopedia, ed., LusoBrasileiro (Joao Grave, Porto, Ldt. Le11o).
Only adults were allowed to be baptized in the early centuries:
Triple baptism was brought into Iberia by the Visigoths (Aryans) in about the sixth century:
In the first centuries the new converts were baptized, being immersed three times. It seems that the Aryans wished to defend this practice, to sustain their error of the triple nature of God, that is, three separate Gods. Because of this the Counsel of Toledo was called in the 6th century and introduced the practice of single immersion.—FORTUNATO DE ALMEIDA, Historia da Igreja em Portugal (1910), tomo I, p. 79.
During the Dark Ages the medieval church taught that the act of baptism could erase the stain of sin from the soul:
The first sacrament of the church is baptism. It washes the soul from original sin and unites the man to Jesus Christ.—PADRE RAPHAEL BLUTEAU, "Baptism," Vocabulario Portuguese-Latino (Coimbra, Portugal, Clerigo Regular, 1712).
Up to the 14th century the famous painters such as Raphael and others represented the baptism of Christ as by immersion.—Encyclopedia Portugesa III, art., "Baptisterios" (Maximos Lemos Cia, Porto).
Even in the middle of the eighteenth century baptism by immersion was stanchly upheld and defended in at least one recorded Roman Catholic diocese in Portugal:
Concerning baptism, the Bishop of Bragance proclaimed in his pastoral letter of January 23, 1759, that he would baptize by immersion and not by pouring, a custom then being introduced into the diocese; the priest be obliged to do the same on the threat of suspense; and only by order of the Prelate could baptism be performed by pouring.—FORTUNATO DE ALMEIDA, Historia da Igreja ern Portugal (Aprovado, Imprensa Academica, Coimbra, Portugal, 1910), tomo IV, p. 308.