This is the title page of the 1552 edition of the Practica d'Arithmetica of Francesco Ghaligai (d. 1536). The book was originall published in 1521, but this printing, like several other printings, is identical with the original. Its intended audience was merchants, so there are many practical problems dealing with issues of trade. In the sections on algebra, Ghaligai introduces his own notation.
On pages 71 and 72, Ghaligai proposes a new notation for powers of the unknown. Notice on the left hand page that his notation for the second power (censo) is just a square, but the other notations never caught on with other authors. On the right hand page, Ghaligai illustrates the notation by calculating the powers of 2 up to the fifteenth power.
This page illustrates a typical algebra problem and makes some use of the "square" notation for censo.