In the first period, inscriptions were engraved, carved or impressed with sharp instruments, and of patterns characteristic of a graving tool, chisel or other form which could be adapted to particular substances like stone, leaves, metal or ivory plates, wax or clay tablets, cylinders and prisms. The ancient Assyrians even used knives or stamps for impressing their cuneiform writing upon cylinders or prisms of soft clay which were often glazed by subsequent bakings in kilns. The other period was that in which written characters were made with liquids or paints of any kind or color. The liquids (inks) were used in connection with a pen manufactured from a reed (calamus), while the paints were "painted" on the various substances with a brush. The writing executed with both of these instruments was on materials like the bark of trees, cloth, skins, papyrus, vellum, etc. The ancient as well as modern pens, though of many sorts and kinds, are to be classified under two general heads, those which scratch and those which use an ink. There is no authority to dispute the generally conceded fact that the "scratching" instrument was the first one used. Its most popular form seems to have been the stylus or bodkin, which was made of a variety of materials, such as iron, ivory, bone, minerals or any other hard substance, which could be sufficiently sharpened at one end to indent the various materials employed in connection with its use. The other end was flattened for erasing marks made on wax and smoothing it. From it the Italian stilletto took its origin. The stylus is best described in the following lines: "My head is flat and smooth, but sharp my foot, And by man's hand to different uses put; For what my foot performs with art and care, My head makes void, such opposites they are." Relative to the employment of marking instruments which belong to the most venerable antiquity, Noel Humphreys observes: