Images Aside through the Ages

Strickland (1841) credits Anne of Bohemia with popularizing sitting aside.  Women and men sat sideways on animals long before and after Anne's bridal journey to England. She may have spread the fashion within the British Isles. 

Position aside varies with time and with equipment and does not always follow the theories commonly found on the internet.  

1360 Regensburg, Germany. (Pierpont Morgan Museum and Library, New York). 

This 14th century image is the oldest in editor's personal collection consistent with a forward facing seat. The image does not show saddle structure supporting this position. One can easily walk in this position without saddle support. 

Très Riches Heures du Duc de Berry c 1412-1416

One often sees variable equipment and riding styles in the same image. The third rider in green sits a top a red pillion pad. The other women appear to have twisted forward in saddles designed for a sideways seat. The knees and feet on the Duchess (white veil) are level as are her feet suggesting they are resting on a planchette.

The Lady on Horseback and the Lansquenet, Albrecht Dürer 1497

In contrast, the Lady by Durer with a more clearly forward facing seat. This saddle supports the forward facing seat and pre-dates the life of Catherine d'Medici (1519 to 1589 according to Britanica) whom the internet often credits with inventing the forward facing seat.