There sat down, once, a thing on Henry's heart
só heavy, if he had a hundred years
& more, & weeping, sleepless, in all them time
Henry could not make good.
Starts again always in Henry's ears
the little cough somewhere, an odour, a chime.
And there is another thing he has in mind
like a grave Sienese face a thousand years
This refers to some type of memory triggers that make Henry remember the oppression that is the “thing on Henry’s heart.” The next line then goes into a more vivid description of how Henry remembers this oppression. 
Dream Song 29