The Da Vinci Notebooks
To know better the direction of the winds. 531
220:531 : In connection with this text I may here mention a hygrometer, drawn and probably invented by Leonardo. A facsimile of this is given in Vol. I, p. 297 with the note: 'Modi di pesare l'arie eddi sapere quando s'a arrompere il tepo' (Mode of weighing the air and of knowing when the weather will change); by the sponge "Spugnea" is written.