Fresco wall-painting of Priapus, House of Vettii from Pompeii, dated 1AD.
Here we see the god Priapus weighing his phallus, stood next to a basket of fruit. Priapus was a god of fertility, and the symbols of the phallus and fruit represented this.
He was often depicted with an overly-large erect phallus, with crops or sometimes infants in the folds of his robes to demonstrate how he was responsible in ensuring the productivity of crops and new generations- important fertility aspects. He was also thought to be used as an object of protecting properties, too.