A new system of proportional cursive scripts was codified from the tenth to the thirteenth century. In a proportional script, each letter's shape is determined by a fixed number of rhombic (diamond-shaped) dots (fig. 12). A rhombic dot is the shape formed when a calligrapher presses his or her pen to paper in one downward motion, producing the diamond shape. A word written in one of the proportional scripts can vary in size but the letters will always be in strict proportion to one another. There are six proportional scripts (the Six Pens)—naskh, thuluth, muhaqqaq, rayhani, tawqi', and riqa' (fig. 13).
Fig. 12. Calligraphic diagrams of the letters alif and ain using the proportional system based on rhombic dots described above
Fig. 13. Six Pens (proportional scripts), all reading bismillah