At around 1500 in German-speaking lands the word conterfait started to be used to describe a portrait, a likeness or an imitation. Soon its equivalents in other languages emerged. New techniques of reproduction and multiplication disseminating rapidly at the time of the print revolution brought about the notion of conterfait as suitable to characterize a credible likeness, i.e. an image representing the actual appearance of a person or a thing. Conterfait thus can be understood as a metaphor for an index, an image produced by means of mechanical impression or a likeness achieved in the presence of the sitter. The appearance of this word in the vocabulary of terms characterizing an image’s relation to reality marks an important caesura: it indicates the moment at which the art of portraiture started to be commonly considered as a skill of producing corporeal likeness. And yet, the question remains: how was the issue of mimesis understood before the print revolution? What role did reality reflected in an image play before the word conterfait came to be used? In an attempt to answer these questions special attention should be paid to one text, Regulae Veteris et Novi Testamenti written around 1390 by Czech priest and ecclesiastic reformer Matej of Janov. Matej, revealing his negative attitude toward images pointed out their material character and emphasized the circumstances of their production, in which a decisive role is played by taste (beneplacito) and invention (fantasia) possessed by the painter. In passing, he also accentuates the role of memory as an important instrument of artistic production and thus identifies mimesis in contemporary images. A painter, according to Matej, creates his works according to his fantasmata, the images of things that he himself saw and heard. They are impressed in the treasury of his memory and he can use them according to his own will, as it pleases him. Portraiture must therefore be understood in terms of memorizing and reworking the elements of reality by the artist rather than as a simple reflection of a sitter’s outward appearance. This can be shown in many portraits executed at from about the time of Matej’s Regulae. Images of Charles IV, Holy Roman Emperor and King of Bohemia, the portrait of Rudolf IV, Archduke of Austria in Vienna, and the portrait of Sigismund of Luxemburg, Holy Roman Emperor and King of Hungary, also in Vienna should be interpreted not as simple reflections of their appearances but rather as studies based on both the observation of nature and the work performed by the artists’ intellect. Thus the art of medieval portraiture appears to be a complex process engaging specific qualities of the artist’s mind, his fantasia and beneplacito.