There is an interesting article on Altar Cards & Last Gospels. The image above shows the extreme caricature, of extra-large cards presumably for a priest with poor eyesight. The three altar cards have become as traditional a feature of post-Tridentine altars as vases of flowers, central tabernacles (often enormous in size with a throne for the monstrance) and gradines.
I won’t “meme” Rad Trad’s article here. You can read it directly through the link above.
I am glad to be of cradle-Anglican background and drawn to the Dearmer revival of medieval altars, sobriety and clean lines. I wrote a comment:
I still have a small sheet of paper lying on the altar near the crucifix (I have a hanging pyx) to act as a prompt for the offertory prayers and the placeat prayer. My altar is so nice and uncluttered without altar cards. Same with flowers – I won’t have them on the altar, just a single vase away from the altar for major feasts.
Murphy’s Law often dictates that you forget the words of something when you don’t have at least a “prompt”! I could make do simply with having the order of mass available, but the bit of paper is practical. Occasional celebrants of a given rite of Mass need more, and turning to the relevant page in the missal is awkward. It is understandable how altar cards came about. However, I do think there is something wrong when they are excessively large or decorated.
The Last Gospel said at the altar was an innovation of 1570. Prior to then, the Prologue of St John was said from memory by the priest on his way back to the sacristy after the end of Mass as a private devotion, as in Pontifical Mass in the Roman rite. Sarum is no exception to the pre-Tridentine rule. One trick is to learn the first few verses, pause while getting to the sacristy and resuming from a card or paper. I don’t find it easy to learn texts by heart, so I sympathise with these practical aspects.