Mannite,

Chambers's Encyclopaedia, Volume 7: Maltebrun to Pearson, p. 25

Mannite, C_6H_8(OH)_6, is a peculiar saccharine matter which forms the principal constituent of Manna (q.v.); it is also found in several kinds of fungi, in asparagus, celery, onions, &c. It is most readily obtained by digesting manna in hot alcohol.

Source scan(s): p. 0034