Avodah Zarah, Chapter Four, Mishnah Two
Mishnah two continues to discuss items that are found in proximity to the mercurius idol, and whether or not these items are assumed to have been used in idolatrous worship and therefore prohibited.
1) If he found on top [of a mercurius] a coins or a garment or utensils behold these are permitted;
2) [But if he found] grape-clusters, wreaths of grain, [gifts of] wine, oil or fine flour, or anything resembling what is offered upon the altar, such is prohibited.
In the previous mishnah we learned that one typical way of worshipping the mercurius idol was to lay stones next to it. In todays mishnah we see ways in which mercurius was not worshipped. It was not worshipped by having money, clothes or other vessels laid next to it. Since this is not typical mercurius worship, it is permitted for Jews to use these items.
However, if anything that is normally sacrificed is found next to a mercurius, these items are forbidden to Jews. Since these items are generally used in idol worship, and evidently also in the worship of mercurius, they are forbidden if they are found in proximity to the idol.