Analysis of I reckon—when I count it all

I reckon—when I count it all—
First—Poets—Then the Sun—
Then Summer—Then the Heaven of God—
And then—the List is done—

But, looking back—the First so seems
To Comprehend the Whole—
The Others look a needless Show—
So I write—Poets—All—

Their Summer—lasts a Solid Year—
They can afford a Sun
The East—would deem extravagant—
And if the Further Heaven—

Be Beautiful as they prepare
For Those who worship Them—
It is too difficult a Grace—
To justify the Dream—