From Walden

When a man is warmed by the several modes which I have described, what does he want next? Surely not more warmth of the same kind, as more and richer food, larger and more splendid houses, finer and more abundant clothing, more numerous incessant and hotter fires, and the like. When he has obtained those things which are necessary to life, there is another alternative than to obtain the superfluities; and that is, to adventure on life now, his vacation from humbler toil having commenced. The soil, it appears, is suited to the seed, for it has sent its radicle downward, and it may now send its shoot upward also with confidence. Why has man rooted himself thus firmly in the earth, but that he may rise in the same proportion into the heavens above?—for the nobler plants are valued for the fruit they bear at last in the air and light, far from the ground, and are not treated like the humbler esculents, which, though they may be biennials, are cultivated only till they have perfected their root, and often cut down at top for this purpose, so that most would not know them in their flowering season.