A foretelling, a prophecy; a prefiguring. Also in Emerson's terminology: the pre-existing poetic essence of a thing.
Origin
Early 17th century (in an earlier sense). From post-classical Latin praecantation-, praecantatio incantation (Vetus Latina), prophecy (in an undated glossary) from classical Latin praecantāt-, past participial stem of praecantāre to recite or chant spells over, in post-classical Latin also to prophesy + -iō.