What are some examples of literature that support the quote, "Stone walls do not a prison make, nor iron bars a cage"
I understand that this is a metaphor for how you look at the situation, but I would like some pieces of literature that support this.
1984--In Orwell's novel, Winston Smith (the protagonist) is eventually arrested and confined in a literal prison. However, he spends much of the novel being imprisoned by fear of and enslavement to Big Brother and the Thought Police. Even when he enjoys his rendezvous with Julia, he realizes that there is no escape for him or her from their totalitarian society. At the end of 1984, Orwell presents a different interpretation of the quote that you cited, for Winston sits free from prison in a tiny pub, drinking as much as he wants, spending his days lazily, and even possessing the freedom to see and talk to Julia if he so desires. Ironically, by this time, Winston's ability to think for himself has been imprisoned, and so while he is physically free once again, he is actually more mentally and psychologically confined than he was at the novel's beginning.
A Thousand Splendid Suns by Khaled Hosseini--In Hosseini's second novel, one of the main characters, Mariam, lives her entire life (except for the last year of it), imprisoned by her insecurities and her husband's abuse. She sees herself as unworthy and so she imprisons her own emotions behind a cold exterior until she finally finds the courage to stand up for her husband's young second wife (Laila) and begins to care for her and Laila's children.
The Count of Monte Cristo--Near the beginning of Dumas' novel, Edmund is literally imprisoned and plots incessantly to make his escape until he actually does so. However, even when he is a free man determined on exacting revenge upon all who betrayed him or who were responsible for his physical imprisonment, he is chained by his vengeful emotions and really cannot enjoy his freedom. It is not until the novel's end when he realizes that revenge will not bring happiness that he is able to free himself to love and live a contented life.
If you're looking for literature that features prisons that are not made of stone or steel, Kate Chopin's "The Story of an Hour," a short story, or The Awakening, a novel, would fit your needs. Both feature women trapped in a man's world. They would be similar in this respect to Madame Bovary.
If you're looking for works in which a character manages to achieve freedom of a sort in his/her mind, even though imprisoned, you could check The Night Thoreau Spent in Jail, or The Count of Monte Cristo. Both feature imprisoned characters that handle imprisonment in unusual ways.
Essentially, it seems to me that you are searching for examples of literature that reflect how imprisonment is not something which is physically imposed. I would say that Flaubert's Madame Bovary would be an example where imprisonment is not physical nor a structure that is imposed on Emma. Rather, the weight of her own dreams and how objective reality fails miserably to reflect them help to imprison Emma. In this sense, the hope of a garden matched with the reality of a desert proves to be quite imprisoning to her. This is not something that is physical, but rather of her own mental creation. Arthur Miller's "Death of a Salesman" might be another example of demonstrating how the idea of a prison or cage is not something externally imposed. Wily's desire to "make it big," to strive for a dream that is hopelessly out of his reach helps to create a prison of sorts for him.