“He who is contented is rich.”

Source: Who Is Man? (1965), Ch. 5<!-- Disavowal of transcendence, p. 83 -->
Context: As a result of letting the drive for power dominate existence, man is bound to lose his sense for nature's otherness. Nature becomes a utensil, an object to be used. The world ceases to be that which is and becomes that which is available.
It is a submissive world that modern man is in the habit of sensing, and he seems content with the riches of thinghood. Space is the limit of his ambitions, and there is little he desires besides it. Correspondingly, man’s consciousness recedes more and more in the process of reducing his status to that of a consumer and manipulator. He has enclosed himself in the availability of things, with the shutters down and no sight of what is beyond availability.

The point of this saying is not that poverty is a virtue, but that happiness does not come with wealth, but from setting limits to one’s desires, and living within those limits with satisfaction.
In [Rubin, Gary, Your Emotional Fitness: Everything You Need to Know to Live a Life of Abundance, http://books.google.com/books?id=CGqu8-5W7UUC&pg=PA173, April 2013, Balboa Press, 978-1-4525-7059-4, 173–].

The Aristos (1964)
Context: The artefacts of a genius are distinguished by rich human content, for which he forges new images and new techniques, creates new styles. He sees himself as a unique eruption in the desert of the banal. He feels himself mysteriously inspired or possessed. The craftsman, on the other hand, is content to use the traditional materials and techniques. The more self-possessed he is, the better craftsman he will be. What pleases him is skill of execution. He is very concerned with his contemporary success, his market value. If a certain kind of political commitment is fashionable, he may be committed; but out of fashion, not conviction. The genius, of course, is largely indifferent to contemporary success; and his commitment to his ideals, both artistic and political, is profoundly, Byronically, indifferent to their contemporary popularity. <!-- no. 61

"Auctorial Induction"
The Certain Hour (1916)
Context: Thus he labors, and loudly they jeer at him; — That is, when they remember he still exists. Who. you ask, is this fellow? — What matter names?
He is only a scribbler who is content.

Source: Aphorisms and Reflections (1901), p. 255

"Symphony", in Memoir of William Henry Channing (1886) by Octavius Brooks Frothingham, p. 166.
Context: To live content with small means; to seek elegance rather than luxury, and refinement rather than fashion: to he worthy, not respectable; and wealthy, not rich; to study hard, think quietly, talk gently, act frankly; to have an oratory in my own heart, and present spotless sacrifices of dignified kindness in the temple of humanity; to spread no opinions glaringly out like show-plants, and yet leave the garden gate ever open for the chosen friend and the chance acquaintance: to make no pretenses to greatness; to seek no notoriety; to attempt no wide influence; to have no ambitious projects; to let my writings be the daily bubbling spring flowing through constancy, swelled by experiences, into the full, deep river of wisdom; to listen to stars and buds, to babes and sages, with open heart; to bear all cheerfully, do all bravely, await occasions, hurry never; … in a word, to let the spiritual, unbidden and unconscious, grow up through the common. This is to be my symphony.

Quod siquis vera vitam ratione gubernet,
divitiae grandes homini sunt vivere parvo
aequo animo; neque enim est umquam penuria parvi.
Book V, lines 1117–1119 (tr. Rouse)
De Rerum Natura (On the Nature of Things)

Poem Sweet Content http://www.bartleby.com/101/204.html