"command that these gifts be borne by the hands of your holy Angel to your altar on high" (the Supplices te rogamus)

"we do not call Paul's tongue or his paper and ink the body and blood of Christ, nor the significant sounds made by his tongue, nor the meaningful signs written on the pages of his letters, but only that which is taken from the fruits of the earth, and consecrated by mystic prayers, and taken by us for our spiritual salvation in memory of what the Lord suffered for us. The hands of men give this its visible appearance, but it can only be consecrated into being such a great sacrament by the invisible working of the spirit of God. For all the physical movements involved in the whole action are worked by God acting in the first place on what is invisible in the ministers, namely on the souls of men or on the services of the occult spirits who are subject to him."

     St. Augustin, De Trinitate III.4.10, trans. Edmund Hill, WSA I/5 (1991), 132-134.  Footnote at the end here:  "This strange little excursus into eucharistic theology throws an interesting light on Augustine's ideas on the subject, and must modify to some extent the impression we get of them, say from his commentary on John 6 (Homilies on the Gospel of John 26, 13-20). Augustine is customarily thought of, largely on the strength of that passage, as holding a 'symbolist' view of the sacrament as against the 'realist' view expressed for example by Ambrose in his De Mysteriis 9. On the whole this is true, as Augustine always lays great stress on the significance of the sacraments, which he classifies as signs, sacred signs, rather than as just things. In this he is firmly taken up by Thomas Aquinas, and again by the leading spirits in theology today, who are reacting, perhaps over-reacting, against a somewhat uncritical and mechanical 'realism' that has colored Catholic sacramental thought and piety for rather a long time.
     "But this passage of ours here shows that Augustine's 'symbolism' was not unqualified. He does indeed introduce the eucharist quite unequivocally in a 'signs' context here. But then he introduces this section, which is in reality a footnote, to explain that the eucharist is a quite unique sort of sign, in that it is to be identified with the thing signified (the body and blood of Christ) in a way that no other sign can be. Furthermore a real and unique spiritual, divine, causality needs to be brought into play to effect this unique sign. It is interesting to observe that he thinks angels might well be co-ministers of the eucharist. Are they thought of perhaps as playing the same kind of role as the mysterious angel in the Supplices te rogamus prayer of Eucharistic Prayer I (the Roman Canon)?"

     I was put onto this passage (though not this translation with this footnote) by A. Sage, "Saint Augustine et la prière du Canon 'Supplices te rogamus…'," Revue des études byzantines 11 (1953):  253 (252-265).  And Sage was very clearly thinking so back then.  The Supplices te rogamus, "so disconcerting for more than one theologian or liturgist" (Sage, 252), I was glad to read:

In humble prayer we ask you, almighty God: command that these gifts be borne by the hands of your holy Angel to your altar on high in the sight of your divine majesty, so that all of us, who through this participation at the altar receive the most holy Body and Blood of your Son, may be filled with every grace and heavenly blessing.  Through Christ our Lord.  Amen.

Supplices te rogamus, omnipotens Deus: iube haec perferri per manus sancti Angeli tui in sublime altare tuum, in conspectu divinae maiestatis tuae; ut, quotquot ex hac altaris participatione sacrosanctum Filii tui Corpus et Sanguinem sumpserimus, omni benedictione caelesti et gratia repleamur. Per Christum Dominum nostrum. Amen.