Sotah, Chapter Three, Mishnah One
Numbers 5:25 reads, Then the priest shall take from the womans hand the meal offering of jealousy, and wave the meal-offering before the Lord, and present it on the altar. Our mishnah explains and paraphrases this verse.
Interestingly, the Mishnah never describes the rubbing out of Gods name, although this is alluded to. Perhaps the activity was too frightful to even be described.
He takes her meal-offering out of the basket of palm-twigs and places it in a ministering vessel and sets it upon her hand.
And the priest places his hand under hers and waves it.
Above in mishnah one we learned that the meal offering was in the womans hands, in a basket of palm twigs. The priest now takes the offering and puts it in a ministering vessel, one of the normal vessels used in the Temple, as is customary for all meal offerings.
The Torah does not state that the woman aids in the waving of the meal offering. However, the rabbis learned that all meal offerings are jointly waved by their owners and by the priest.