from the mailing list of chiasmus

THIS WEEK'S PUZZLER:

On December 12, 1889, this English poet died in Venice at age 77. In an 1855 poem he penned the immortal oxymoronic words "less is more," a saying eventually popularized by the German-born architect Ludwig Mies Van der Rohe. He also authored this legendary inspirational line:

"Ah, but a man's reach should exceed his grasp.
Or what's a heaven for?"

Who is the author?

(Answer in the comments)