Tolkien once described Legolas (this quote can be found reproduced in
The Book of Lost Tales) when reacting to an artist's depiction of his character...
'He was tall as a young tree, lithe, immensely strong, able swiftly to draw a great war-bow and shoot down a Nazgūl, endowed with the tremendous vitality of Elvish bodies, so hard and resistant to hurt that he went only in light shoes over rock and through snow, the most tireless of all the Fellowship.' JRRT
I think this can be found in part II, IIRC.