Codex on the Flight of Birds

In 1505 Leonardo filled a pocket notebook with observations on birds: how they turn the wing to the wind, how they shift their weight to keep balance, how the kite steers with its tail. The pages are crowded with small sketches drawn as he watched.

He hoped to use the knowledge for a flying machine, the "great bird", which he wanted to launch from Monte Ceceri near Fiesole. There is no evidence he ever tried. One page carries, faintly under the notes, a red chalk sketch of a man's head that some believe is his own.

The codex left Italy after his death, was split up, and the sheets were reassembled in the nineteenth and twentieth centuries.