A Lark In A Cage [Webster]

From John Webster, The Duchess of Malfi (1614), IV.ii.

Duchess: Thou art not mad, sure: dost know me?
Bosola: Yes.
Duchess: Who am I?
Bosola: Thou art a box of worm-seed, at best but a salvatory of green mummy. What's this flesh? a little crudded milk, fantastical puff-paste. Our bodies are weaker than those paper-prisons boys use to keep flies in; more contemptible, since ours is to preserve earth-worms. Didst thou ever see a lark in a cage? Such is the soul in the body: this world is like her little turf of grass, and the heaven o'er our heads like her looking-glass, only gives us a miserable knowledge of the small compass of our prison.
Duchess: Am not I thy duchess?