The Collaborative International Dictionary of English v.0.48:

Mantua \Man"tu*a\, n.
   1. A superior kind of rich silk formerly exported from Mantua
      in Italy. [Obs.] --Beck (Draper's Dict.).
      [1913 Webster]

   2. A woman's cloak or mantle; also, a woman's gown. [Obs.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

mantua
    n 1: loose gown of the 17th and 18th centuries