Diodoros Sikeliotes, Library of History 4.24.1-6
After this Heracles, as he passed through the plain of Leontini, marveled at the beauty of the land, and to show his affection for the men who honoured him he left behind him there imperishable memorials of his presence. And it came to pass that a peculiar thing took place near the city of Agyrium. Here he was honoured on equal terms with the Olympian gods by festivals and splendid sacrifices, and though before this time he had accepted no sacrifice, he then gave his consent for the first time, since the deity was giving intimations to him of his coming immortality. For instance, there was a road not far from the city which was all of rock, and yet the cattle left their tracks in it as if in a waxy substance. Since, then, this same thing happened in case of Heracles as well and his tenth Labour was likewise coming to an end, he considered that he was already to a degree participating in immortality and so accepted the annual sacrifices which were offered him by the people of the city. Consequently, as a mark of his gratitude to the people who had found favour with him, he built before the city a lake, four stades in circumference, which he ordained should be called by his name; and he likewise gave his name to the moulds of the tracks which the cattle had left in the rock and dedicated to the hero Geryones a sacred precint which is honoured to this day by the people of that region. To Iolaüs, his nephew, who was his companion on the expedition, he likewise dedicated a notable sacred precinct, and ordained that annual honours and sacrifices should be offered to him, as is done even to this day; for all the inhabitants of this city let the hair of their heads grow from their birth in honour of Iolaüs, until they have obtained good omens in costly sacrifices and have rendered the god propitious. And such a holiness and majesty pervade the sacred precinct that he boys who fail to perform the customary rites lose their power of speech and become like dead men. But so soon as anyone of them who is suffering from this malady takes a vow that he will pay the sacrifice and vouchsafes to the god a pledge to that effect, at once, they say, he is restored to health. Now the inhabitants, in pursuance of these rites, call the gate, at which they come into the presence of the god and offer him these sacrifices, “The Heracleian,” and every year with the utmost zeal they hold games which include gymnastic contests and horse-races. And since the whole populace, both free men and slaves, unite in approbation of the god, they have commanded their servants, as they do honour to him apart from the rest, to gather in bands and when they come together to hold banquets and perform sacrifices to the god.
Diodoros Sikeliotes, Library of History 5.2.5
Indeed, in the plain of the Leontini, we are told, and throughout many other parts of Sicily the wheat men call “wild” grows even to this day. And, speaking generally, before the corn was discovered, if one were to raise the question, what manner of land it was of the inhabited earth where the fruits we have mentioned appeared for the firs time, the meed of honour may reasonably be accorded to the richest land; and in keeping with what we have stated, it is also to be observed that the goddesses who made this discovery are those who receive the highest honours among the Siceliotae.