Poets are not any better at translating than people who are merely Spanish professors. I would say they tend to be worse. One I found today from British poet Charles Tomlinson, was
We the rivers who supply
with transitory lives the sea
of death... what lines they are!
This is supposed to be Machado's gloss on Manrique's "que van a dar en el mar..."
Nuestras vidas son los ríos
que van a dar a la mar
que es el morir... ¡Gran cantar!
[our lives are the rivers / that give out in the sea / that is dying. Great song]. It is hard to know where to begin. Manrique's lines are so iconic. To call them "lines" rather than "song," like Machado does, is strike one.
Another poet, Bly, doesn't do all that much better, but at least has some respect for the original:
"Our lives are rivers
and rivers flow and move to the sea,
which is our dying." Marvelous lines!
I don't have a perfect translation for "van a dar a la mar." There can be no supplying, though, or sea of death or transitory lives. What is charming in Manrique is the simplicity and naivete: he is telling you what the symbols mean directly. There is no obfuscation.
I guess I am objecting to free translation, if the the results are so piss-poor.
[UPDATE: Longfellow has
|Our lives are rivers, gliding free|
|To that unfathomed, boundless sea,|
|The silent grave!|