An 18th-century scientific engraving, labeled Tabula VII, features two distinct technical diagrams arranged vertically. The top diagram, Fig. I, depicts a complex, semi-circular mechanical apparatus that resembles a large scale or measuring instrument. It consists of a curved, tiered base with numerous small, dark circular openings and vertical lines, supported by a wooden frame. A piano keyboard is visible at the bottom of the apparatus. Above this base, three groups of dotted lines extend upward from the openings toward three concentric circles. At the top right of the apparatus, the text "pag. 354" is printed. The bottom diagram, Fig. II, shows a horizontal layout of various components: on the left, a concave surface, a candle flame, and three lenses are marked from left to right with the script capital letters H, G, X, I, and the lower case letter i; dotted lines extend from these to the right; and on the right, where the dotted lines meet an oval shape. The entire print is rendered in fine black lines on aged, off-white paper, with a vertical color calibration strip placed along the right edge of the document for archival reference.