DGR's source is the text in
Poeti
del Primo Secolo
As with most of DGR's translations, this one cannot be exactly fixed. It is probably a fairly early work, however—done in the late 1840s.
The translation was first published in 1861 in
The
Early Italian Poets
Dante
and his Circle
Early Italian Poets
Poeti
del primo secolo
Poeti de duecento