Breve et facile maniera d’essercitarsi a far passaggi
Like many of its contemporary sources it uses an example of two notes (an interval) and then shows how you could use an ornament to go from one note to the next. In a type of table-format the book suggests several options for the same interval; by learning those by heart you get a sense for the style and possibilities.
In this book it's interesting that Conforti shows within the same diminution how there are different options. Furthermore, with the + sign he shows which ornament is easiest to use, in that you don't have to know counterpoint to know whether you will make a mistake or not.
A translation and modern edition can be bought here:
Solo / Ensemble
Giovanni Luca Conforti
Type of Thing you Learn
Diminutions, Diminution, Ornamentation, Passaggi, Cadenze,
Beginner, (More) Advanced