How far is it to Heaven — Divine Comedy

The key word is Topography at the end. None of Dickinson's death-like poems is really about death. This poem talks about The Divine Comedy. Dickinson's family library has the version translated by Cary, The Vision: or Hell, Purgatory, and Paradise (1845).

How far is it to Heaven? ¹
As far as Death this way－
Of River or of Ridge beyond
Was no discovery.

How far is it to Hell? ⁵
As far as Death this way－
How far left hand the Sepulchre
Defies Topography.

(F.965/J.929)

[1, 5] to Heaven, to Hell:: Dante's journey to hell, purgatory, and heaven.
[2, 6] Death this way:: in the book the way to the heaven is through hell.
[3, 4] River, ridge, no discovery:: these landscapes do not exist.
[7] left hand:: left-handed, ambiguous, questionable _{(OED 3)}; the geography in the book is questionable.
[8] Defies Topography:: the geography described in the book was a challenge of topography.