306. For only what is required for the celebration of the Mass may be placed on the altar table: namely, from the beginning of the celebration until the proclamation of the Gospel, the Book of the Gospels; then from the Presentation of the Gifts until the purification of the vessels, the chalice with the paten, a ciborium, if necessary, and, finally, the corporal, the purificator, the pall, and the Missal.
In addition, arranged discreetly, there should be whatever may be needed to amplify the Priest’s voice.
One finds that discreet microphone less and less these days.
307. The candlesticks required for the different liturgical services for reasons of reverence or the festive character of the celebration (cf. no. 117) should be appropriately placed either on the altar or around it, according to the design of the altar and the sanctuary, so that the whole may be harmonious and the faithful may not be impeded from a clear view of what takes place at the altar or what is placed upon it.
Two would seem to be in keeping with the character of the Roman Rite most of the time. The guiding principles of harmonious design and giving the assembly a clear view are not always considered when indulging the modern fad for six candles.
308. Likewise, either on the altar or near it, there is to be a cross, with the figure of Christ crucified upon it, a cross clearly visible to the assembled people. It is desirable that such a cross should remain near the altar even outside of liturgical celebrations, so as to call to mind for the faithful the saving Passion of the Lord.
This would be another modern challenge. As an object of veneration, reverence, and reference, the cross probably should be a separate piece. In one college chapel I visited, I noted the cross was flat on the altar mensa. Facing the priest, of course.
My parish has one optimal design: a stand-alone piece used for veneration, placed for the view of all.