Please see Academy of Saint Gabriel report 2903 for references to the source of each image.
Other medieval drawings of ermine tails can be found in A. C. Fox-Davies' book The Art of Heraldry, p.49; the ones on the top row are probably appropriate for the 14th century. Slightly later examples appear in the Edward IV roll, from the 1460's. Some 14th century German drawings appear in The Zurich Roll; #32 on this page contains ermine (bottom left in the first image).