If your Nerve, deny you—
Go above your Nerve—
He can lean against the Grave,
If he fear to swerve—
That's a steady posture—
Never any bend
Held of those Brass arms—
Best Giant made—
If your Soul seesaw—
Lift the Flesh door—
The Poltroon wants Oxygen—
Nothing more—
Poltroon  is a 16th century word meaning fool or coward. It has etymological roots to the Latin  pullus  meaning young animal. Dickinson suggests that the fool is focused only his  animal  survival; using oxygen, breathing, as a representation of this, she describes the opening of the mouth as the lifting of a flesh door. 
 She mocks the naïvety of these fools struggling to delve into introspection of the self. Dickinson suggests if you’re having trouble confronting yourself, you will just have to enjoy your meaningless “nothing more”.
If your Nerve deny you 292