In the poem "Criminal Ballad", Ted Hughes describes a chain of tragedies happening in parallel with a man's simple moments of life. One of these is the following:
And when he ran and got his toy squealing with delight
An old man pulled from under the crush of metal
Gazed towards the nearby polished shoes
And slowly forgot the deaths in Homer
The sparrowfall natural economy
Of the dark simple curtain
I'm trying to understand how the images in the last two lines are related to each other. So, the "sparrowfall" image is easy:
"'Sparrowfall' refers us to Matthew 10:29, where Christ is comforting the disciples by telling them that God's providence [...] covers everything, even the smallest details such as man himself would forget. For Hughes, this is no comfort to the old man at his death."
— Craig Robinson (1989). Ted Hughes As Shepherd Of Being, p. 61. Palgrave Macmillan.
Also, it might be helpful to note that Hamlet makes the same biblical reference, saying that "there is a special providence in the fall of a sparrow".
Then, when reading Matthew 10:29, we can also see that the "sparrowfall" is given in the context of commerce, and thus we can understand the meaning of "natural economy":
Are not two sparrows sold for a farthing? and one of them shall not fall on the ground without your Father.
— Matthew 10:29, King James Bible
But what does a "dark simple curtain" have to do with it?