Nicene and Post-Nicene Fathers, Ser. II, Vol. XIV:
The Canons of the Council in Trullo; Often Called The Quinisext Council.: Canon LXXIII

p. 398 Canon LXXIII.

Since the life-giving cross has shewn to us Salvation, we should be careful that we render due honour to that by which we were saved from the ancient fall.  Wherefore, in mind, in word, in feeling giving veneration (προσκύνησιν) to it, we command that the figure of the cross, which some have placed on the floor, be entirely removed therefrom, lest the trophy of the victory won for us be desecrated by the trampling under foot of those who walk over it.  Therefore those who from this present represent on the pavement the sign of the cross, we decree are to be cut off.

Notes.

Ancient Epitome of Canon LXXIII.

If there is a cross upon a pavement it must be removed.

This canon defines that to the image of the cross is to be “given veneration (προσκύνησις) of the intellect, of the words, and of the sense,” i.e., the cross is to be venerated with the interior cultus of the soul, is to be venerated with the exterior culture of praise, and also with sensible acts, such as kissings, bowings, etc.