What do the ancient texts say ?

Julius Caesar referred to the Gauls as follows when Gaul had recently been conquered (mid-Ist century BC):
"They worship as their divinity, Mercury in particular, and have many images of him, and regard him as the inventor of all arts, they consider him the guide of their journeys and marches, and believe him to have great influence over the acquisition of gain and mercantile transactions."
The Gallic Wars, book VI, ยค 17 (translation W.A. McDevitte and W.S. Bohn).

Commodianus, a Christian bishop of the 3rd century AD, denigrated the Roman gods in his poems, while describing their traditional image:
"Let your Mercury be depicted with a Saraballum, and with wings on his helmet or his cap, and in other respects naked. I see a marvellous thing, a god flying with a little satchel. Run, poor creatures, with your lap spread open when he flies, that he may empty his satchel: do ye from thence be prepared. Look on the painted one, since he will thus cast you money from on high: then dance ye securely."
The Instructions of Commodianus in Favour of Christian Discipline