Book  (Oct 2001)  Page(s) 125-126.  Includes photo(s).
 
Clematis 'Belle Nantaise'
Auguste Boisselet (France) 1887
Parentage unknown
... single, very large, wide lavender-blue flowers... six sharply pointed tepals... Each tepal carries a slightly lighter blue central bar. White filaments with pale creamy yellow anthers...

Book  (Apr 1998)  Page(s) 126.  

Website/Catalog  (1912)  Page(s) 77.  
 
Summer and Autumn Clematis.
In bloom from July to October.
These flower upon the wood of the current year's growth, and should therefore be pruned to five or six eyes.  
Belle Nantaise, delicate lavender; good...  1s. 6d

Book  (1906)  Page(s) 52.  
 
Principal garden varieties of Clematis:
Lanuginosa type. (July to October.)
Belle Nantaise... Lavender.

Book  (1898)  Page(s) 61.  
 
Variétés Horticoles
1er Groupe.—PATENS
Section II. — Lanuginosa.
Bèlle Nantaise (Boisselot).  Très large fleur d'un beau bleu lavande.