in Thoreau’s Journal:
It is wise to write on many subjects, to try many themes, that so you may find the right and inspiring one. Be greedy of occasions to express your thought. Improve the opportunity to draw analogies. There are innumerable avenues to a perception of the truth. Improve the suggestion of each object however humble, however slight and transient the provocation. What else is there to be improved ? Who knows what opportunities he may neglect? It is not in vain that the mind turns aside this way or that: follow its leading; apply it whither it inclines to go. Probe the universe in a myriad points. Be avaricious of these impulses. You must try a thousand themes before you find the right one, as nature makes a thousand acorns to get one oak. He is a wise man and experienced who has taken many views; to whom stones and plants and animals and a myriad objects have each suggested something, contributed something.