The Baron in the Trees by Italo Calvino:
If youth vanishes quickly on the earth, just imagine in the trees, whence everything is fated to fall: leaves, fruits. Cosimo was becoming old. So many years, with all the nights spent in the cold, in the wind, in the rain, in frail shelters or none, in the open air, with never a house, a fire, warm food… Cosimo was now a shrunken old man, legs bowed, arms long, like a monkey, hunchbacked, bundled up in a fur cloak with a hood, like a furry friar. His face was burned by the sun, wrinkled as a chestnut, with light round eyes amid the wrinkles.