Watermarks - Islamic manuscripts

Drawing of the human organ of speech: a cross-section of the mouth.
Indicated are the articulation points of the Arabic phonemes, as part of
the preliminary pages of an Acehnese Qur’ân of the 19th century. In
non-arabophone regions (Turkey, South-East Asia, etc.) one may find
similar explanations of Arabic phonology. On the left side a poem in
Malay telling how to recite the Qur’an. Source: MS Leiden, Or. 2064, f. 4a