Ten historic hygrometers, psychrometers, and humidity recorders shown with verified Wikimedia Commons photographs. Photograph credits: 1. File:Hygrometer, Germany, c. 1890 - Museum of Science and Industry (Chicago) - DSC06359.JPG; Daderot; CC0; http://creativecommons.org/publicdomain/zero/1.0/deed.en; https://commons.wikimedia.org/wiki/File:Hygrometer%2C_Germany%2C_c._1890_-_Museum_of_Science_and_Industry_%28Chicago%29_-_DSC06359.JPG; 2. File:Haar-Hygrometer.jpg; Daniel FR at de.wikipedia.org; Public domain; ; https://commons.wikimedia.org/wiki/File:Haar-Hygrometer.jpg; 3. File:Haar-Hygrometer (Firma Fischer).jpg; Rhetos; CC0; http://creativecommons.org/publicdomain/zero/1.0/deed.en; https://commons.wikimedia.org/wiki/File:Haar-Hygrometer_%28Firma_Fischer%29.jpg; 4. File:Hair hygrometer-MHS 106-P5200227-black.jpg; Rama; CC BY-SA 3.0 fr; https://creativecommons.org/licenses/by-sa/3.0/fr/deed.en; https://commons.wikimedia.org/wiki/File:Hair_hygrometer-MHS_106-P5200227-black.jpg; 5. File:Whirling psychrometer, 1950s - Science Museum, London.jpg; The wub; CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0; https://commons.wikimedia.org/wiki/File:Whirling_psychrometer%2C_1950s_-_Science_Museum%2C_London.jpg; 6. File:Sling psychrometer.JPG; User:CambridgeBayWeather; Public domain; ; https://commons.wikimedia.org/wiki/File:Sling_psychrometer.JPG; 7. File:Psychrometer fan for simple hygrometer, c. 1965 - Museum of Science and Industry (Chicago) - DSC06382.JPG; Daderot; CC0; http://creativecommons.org/publicdomain/zero/1.0/deed.en; https://commons.wikimedia.org/wiki/File:Psychrometer_fan_for_simple_hygrometer%2C_c._1965_-_Museum_of_Science_and_Industry_%28Chicago%29_-_DSC06382.JPG; 8. File:BaroThermoHygrograph.JPG; Harke; CC BY-SA 3.0; https://creativecommons.org/licenses/by-sa/3.0; https://commons.wikimedia.org/wiki/File:BaroThermoHygrograph.JPG; 9. File:Thermohygrograph.jpg; Hafenbar at German Wikipedia; CC BY-SA 3.0; http://creativecommons.org/licenses/by-sa/3.0/; https://commons.wikimedia.org/wiki/File:Thermohygrograph.jpg; 10. File:Dunmore Hygrometer Sensor 1938.jpg; National Institute of Standards and Technology (NIST); Public domain; ; https://commons.wikimedia.org/wiki/File:Dunmore_Hygrometer_Sensor_1938.jpg;