The court astrologer sold ‘wisdom water’ that promised eloquence. Tenali poured it out and replaced it with actual water; sales did not change.
At the next court, Tenali served the same water to the king and a stable boy. “One speaks wisely after drinking; the other still smells of horses,” he said. “The miracle is not in the cup.” The astrologer’s stall closed; the stable boy learned letters at the king’s expense and later taught others to drink from quieter wells.