Immanuel Kant. Aquatint silhouette by J.T. Puttrich, 1793. https://www.rawpixel.com/image/13998894/immanuel-kant-aquatint-silhouette-jt-puttrich-1793Free Image from public domain licenseImmanuel Kant. Line engraving by E. Wagner after B. Schwartz. https://www.rawpixel.com/image/13992058/immanuel-kant-line-engraving-wagner-after-schwartzFree Image from public domain licensePhrenological chart with three figures of a head and sketches of the heads of famous men. Coloured lithograph, 1836. https://www.rawpixel.com/image/13992613/image-paper-cartoon-faceFree Image from public domain licenseJohn Gregory. Stipple engraving by W. Ridley, 1804, after F. Cotes, 1764. https://www.rawpixel.com/image/13982083/john-gregory-stipple-engraving-ridley-1804-after-cotes-1764Free Image from public domain license