DGR wrote the lines in June 1867 for a picture he was doing of Frederick Leyland's wife (see his letter to Leyland of 18 June 1867, Fredeman,
DGR's translation is adapted from a triplet by Angelo
Poliziano (1454-1494). Rossetti translated the lines into English, and then
appears to have re-translated it into French, and then translated the French
into yet another English version.
Copies of Poliziano's text and DGR's translation(s) are in two notebooks, both at Duke: notebook one (which has a different second copy) and notebook three.
First published by WMR in 1911, where an inference might be drawn that the Italian
original was written by Rossetti.