Overall, “la pratica di prospettiua” is structured in 2 “books”, each having multiple chapters.
The first book seems to focus a lot on perspective, proportions, and geometrics. Every spread consists of an explanatory text on the left and drawings on the right side, the latter showing the proposed perspectives and proportions. The text on the left seems to explain the complementary picture on the right. There is also a significant reliance on basic forms like circles and squares. These are being explained on how to be used, scaled, and combined to draw perspectives of certain elements. Funnily enough the elements being shown are not full buildings, they go from columns, arches, spheres to full proportional placements of doors and windows on facades and even string instruments at the end of the first book. Especially the inclusions of those string instruments and other non-architectural elements lead me to the conclusion that the first book is primarily dedicated to being a study or a handbook, explaining the principles of perspective drawing and forms, proportions, and their combination through various types of elements rather focusing solely on architecture. Though I need to clarify that most pictures are of architectural elements and architecture is here the main source for the application of perspective and proportions.
The second book consists of spreads which consist full blown perspective drawings on the right page with the left being empty. The drawings are very detailed and even include shadowing. After displaying various perspective drawings of architectural elements like various capitol orders, arches and even the Tempietto, things get very interesting: The following drawings are basic geometric forms being drawn three-dimensional and in various appearances, from 3D polygons, spiked spheres, “grid only” forms, snowflake like/ star shapes and even just accumulations of random forms. That is where another major topic in Sirigattis work comes in: shadow and light. Especially the spiked shapes demonstrate Sirigattis expertise in perspective and the handling of light and shadow (chiaroscuro).
Being released in 1596, “la pratica di prospettiua” features mainly example from the period like the Tempietto and antique building schemes like Corinthian and Ionic orders, each with shadowing of course.
All in all, the second book seems to work as a “catalogue” of various perspectives, rendered pictures, and many shape studies, in which chiaroscuro is also implemented of course.
Lorenzo Sirigatti, being a member of the same Academy in which Galileo Galilei studied as a young man, brings through his work the tradition of perspective drawing up to Galileo’s time.