in Thoreau’s Journal:    

It is surprising how any reminiscence of a different season of the year affects us. When I meet with any such in my journal, it affects me as poetry, and I appreciate that other season and that particular phenomenon more than at the time. The world so seen is all one spring, and full of beauty.

You only need to make a faithful record of an average summer day’s experience and mood, and read it in the winter, and it will carry you back to more than that summer day alone could show. Only the rarest flower, the purest melody of the season, thus comes down to us.