The perspectograph is a famous instrument that allow to obtain point by point a correct perspective drawing of a threedimensional object. Perspectographs were used by painters and scenographers in XVI and XVII cent. ( but also before by L.B. Alberti). Some types of perpespectograph are very simple (as these reproduced in Dürer's xylographies), some types are rather complex. In our model (of Dürer's perspectograph) the observer who looks through the ocular, sees the pattern drawn on the vertical table exactly superimsposed on the pattern drawn on the orizzontal table.