Paper: 12 rectangles with a ratio of 1 by sqrt(2); here: 7.4 cm by 10.5 cm (3 in by 4 1/4 in)
Model in the collapsed state: diameter of 7.5 cm (3 in)
This video shows how I fold an origami toy called "Vertigo" designed by Francesco Mancini. It's really fun to play with!
Actual folding time: 30 minutes (including explanations)