in Thoreau’s Journal:

The N. side of Walden is a warm walk in sunny weather. If you are sick and despairing, go forth in winter and see the red alder catkins dangling at the extremity of the twigs all in the wintry air, like long, hard mulberries, promising a new spring and the fulfilment of all our hopes. We prize any tenderness, any softening in the winter, catkins, birds’ nests, insect life, etc. The most I get, perchance, is the sight of a mulberry-like red catkin, which I know has a dormant life in it seemingly greater than my own.