Strabo, Geography

Then one comes to the mountain Gallesius, and to Colophon, an Ionian city, and to the sacred precinct of Apollo Clarius, where there was once an ancient oracle. The story is told that Calchas the prophet, with Amphilochus the son of Amphiaräus, went there on foot on his return from Troy, and that having met near Clarus a prophet superior to himself, Mopsus, the son of Manto, the daughter of Teiresias, he died of grief. Now Hesiod revises the myth as follows, making Calchas propound to Mopsus this question:“I am amazed in my heart at all these figs on this wild fig tree, small though it is; can you tell me the number?
”And he makes Mopsus reply:“They are ten thousand in number, and their measure is a medimnus;¹ but there is one over, which you cannot put in the measure.
”² "Thus he spake," Hesiod adds,“and the number the measure could hold proved true. And then the eyes of Calchas were closed by the sleep of death.
”³But Pherecydes says that the question propounded by Calchas was in regard to a pregnant sow, how many pigs she carried, and that Mopsus said, "three, one of which is a female," and that when Mopsus proved to have spoken the truth, Calchas died of grief. Some say that Calchas propounded the question in regard to the sow, but that Mopsus propounded the question in regard to the wild fig tree, and that the latter spoke the truth but that the former did not, and died of grief, and in accordance with a certain oracle. Sophocles tells the oracle in his Reclaiming of Helen, that Calchas was destined to die when he met a prophet superior to himself, but he transfers the scene of the rivalry and of the death of Calchas to Cilicia. Such are the ancient stories.