In Greek mythology, Battus (Ancient Greek Βάττος) is the old herdsman who witnesses Hermes driving off Apollo's cattle. Bribed with a heifer to keep silence, he betrays the secret when Hermes returns in disguise and offers a richer reward; the god turns him to stone — the touchstone that tests gold. Ovid sets him by Neleus' pastures; handbook traditions also place the witness in Arcadia.
Adapted from Wikipedia, "Battus (mythology)" · CC BY-SA 4.0
I.Witness and perjury
On the day of his birth Hermes steals Apollo's herd. Only Battus sees the theft. Hermes leads him aside and promises a cow if he will keep silence; returning in another shape, the god offers a bull and a cow for news of the cattle, and the old man promptly betrays the secret. Hermes petrifies him — in Ovid, into the touchstone that reveals gold.
The atlas id battus-pieria follows the Pierian / Neleian pasture strand of the cattle theft. Wikipedia's short Battus stub stresses an Arcadian Maenalus setting in some handbooks; both are the same oath-breaking witness, not Battus of Cyrene the historical colonist.
II.Homonyms
Do not confuse this mythic herdsman with Battus I of Cyrene or other historical bearers of the name.