In the long winter of 1816, the year without even a summer, there were food riots in the UK and famines in China and red snow falling in Italy, following on an ungenial, incessant rainfall that forced Mary Shelley and her friends to stay inside and write scary stories (Frankenstein being surely an unanticipated consequence of climatic variation).
And Julius Schnorr von Carolsfeld and his friends, the brothers Ferdinand and Friedrich Olivier, passed their time that long long winter in what must be the gentlest competition I've ever known: vying with each other to make precise drawings of dried leaves.
I found Julius' leaves at the blog illustrationart. The other images are sourced from various places around the web; it isn't clear where these drawings make their home. If you have additional information, get in touch.