What great orator put pebbles in his mouth?

When the ancient Athenian orator Demosfhenes (384?-322 B.C.) was a young man he had a frail body, weak lungs and a shrill voice. Plutarch tells us that Demosthenes “had a weakness and a stammering in his voice, and a want of breath, which caused such a distraction in his discourse, that it was difficult for the audience to understand him.” It seems that, among other handicaps, he was unable to pronounce the sound expressed by the letter “r.” The first time the young orator spoke in public his audience laughed at and heckled him. The hesitation and stammering of his tongue he corrected by practicing to speak with pebbles in his mouth; and he strengthened his voice by running or walking uphill, and pronouncing some passage in an oration or a poem, during the difficulty of breath which that caused.” The usual version of this is that Demosthenes overcame his impediment of speech by standing on the shore with pebbles in his mouth and declaimed in competition with the roaring of the sea. “You have stones in your mouth,” is said of a person who stutters or speaks indistinctly.