(A note must be made. For those not interested in this admittedly specialist sort of historical topic, please recall as a liturgical blog we have the luxury to dive into both the greater and the smaller things surrounding the liturgy.)
Liturgical Sandals for Prelates
We turn again to Nainfa's Costumes of Prelates of the Catholic Church according to Roman Etiquette.
A few principles must here be laid down concerning pontifical sandals (sandalia, compagi). These are the footwear used at Pontifical Mass by Bishops and all who have, by law or special concession, the privilege of using the pontifcals.
The shape of these sandals is that of low shoes, with a thin sole and a flat heel. They would be even more correct, and more in conformity with etiquette and tradition, if they had no heel at all. They are fastened with silk ribbons or strings, to the end of which are attached small gold tassels if the Prelate is a Cardinal, a Bishop, or a Protonotary Apostolic di numero or supernumerary; tufts or tassels of silk, if he is of a lower rank.
The Rubric prescribes that the color of the sandals should match that of the vestments, that is the color required by the office of the day; but at Requiem Masses the officiating Prelate does not wear the sandals. These sandals should be made of silk; no Prelate is allowed sandals of velvet or of gold cloth, and the Pope and Cardinals alone have a right to wear sandals embroidered with gold or silver.
Bishops and the Protonotaries Apostolic di numero and supernumerary may wear sandals bordered with a gold or silver strip; but other Prelates who may have the privilege of the pontificals should wear sandals with no other ornament than a border of yellow silk braid.
[...]
The pontifical sandals, as well as the liturgical stockings, are to be used only at High Mass pontifically celebrated; they go together and are pre scribed by the same rubric. A Prelate is no more permitted to waive this rubric under the pretext of simplicity, than to celebrate Mass without the proper vestments.
The privilege of putting on the stockings and sandals at the throne or at the faldstool belongs to the Pope, Cardinals, Bishops, Abbots and the seven Protonotaries Apostolic di numero. The other Protonotaries, Prelates, Canons, etc., who may have been granted the privilege of the pontificals, must put on their sandals in the sacristy.
There is only one prayer to be said by the Prelate while putting on his stockings and sandals, the prayer a "Calcea, Domine, pedes meos". It is not required to repeat it twice.
Non-Liturgical Shoes of Prelates and Clerics
As we are on the topic of shoes, it seems fitting to consider what had been the tradition for prelatial and clerical footwear outside the liturgy.
The ecclesiastical shoe is well known, for it has preserved the general appearance of the footwear in vogue at the beginning of the nineteenth century and still used as part of the court dress a low patent leather shoe, or pump, with a large buckle in front.
Shoes of this kind, according to Roman etiquette, should be worn by all members of the clergy, and by those who have to discharge any ecclesiastical functions in church, as chanters, sacristans, etc. The buckles of the shoes, for the inferior members of the clergy and the officers of the church, are made of polished steel; and for priests, monks, and Prelates belonging to Religious Orders, of silver. Gold or gilded silver buckles are reserved for secular Prelates.
A Cardinal's ordinary shoes are black, with a red border and red heels. When a Cardinal vests in his red cassock and cappa magna, he may wear shoes made entirely of red leather. Etiquette prescribes it at Rome on solemn occasions, for instance, when Cardinals attend solemn Pontifical chapels or consistories.
Papal Shoes
It is well known that the Pope wears for every day shoes, red, thin-soled, flat-heeled slippers, made of cloth or silk, according to the season. On the vamp of these shoes a gold cross is embroidered, which faithful Catholics, admitted to a private audience, kiss after having made three genuflections, according to etiquette.
