"'Tis first"

#700, The Poems of Emily Dickinson: Reading Edition, ed. R. W. Franklin:

The Way I read a Letter's - this -
'Tis first - I lock the Door -
And push it with my fingers - next -
For transport it be sure -

And then I go the furthest off
To counteract a knock -
Then draw my little Letter forth
And slowly pick the lock -

Then - glancing narrow, at the Wall -
And narrow at the floor
For firm Conviction of a Mouse
Not exorcised before -

Peruse how infinite I am
To no one that You - know -
And sigh for lack of Heaven - but not
The Heaven God bestow -