What is "alphitomancy"

Alphitomancy \Al*phit"o*man`cy\, n. [Gr. ? barley meal + -mancy: cf. F. alphitomancie.] Divination by means of barley meal.
--Knowles.

n. An Ancient Greek method of divination using barley meal, used for instance to reveal guilty parties; it entailed feeding a person or group barley meal, and judging those who felt no effects to be innocent, while judging those who felt indigestion to be guilty.

Alphitomancy (from Greek ἄλφιτον alphiton, 'barley', and μαντεία manteia, 'divination') is a form of divination involving barley cakes or loaves of barley bread.

When someone in a group was suspected of a crime, the members of the group would be fed barley cakes or slices of barley bread. Supposedly, the guilty party would get indigestion, while all others would feel well.