Full Idea
Chrysippus praises Diogenes for saying to bystanders as he masturbated in public, "Would that I could thus rub the hunger too out of my belly".
Gist of Idea
Diogenes masturbated in public, wishing he could get rid of hunger so easily
Source
report of Diogenes (Sin) (reports [c.360 BCE]) by Plutarch - 70: Stoic Self-contradictions 1044b
Book Reference
Plutarch: 'Moralia - vol 13 part 2', ed/tr. Cherniss,Harold [Harvard Loeb 1993], p.501
A Reaction
So it is not quite true that people only need corn and water. Diogenes' remark doesn't explain why he did it in public. Was it to defy local convention (as befits a citizen of the world), or was it to teach?