Here are few book scans with directions how to crop ears and diagram for those who can’t read spanish
To the colour photos:
Typical Presa Canario ear cropp. Description from book says:
Upper: ears are cut in shape of triangle, as it is traditional with perros de presa canarios. You can notice the corners.
Lower: ears of adult perro de presa canario. As this photography shows it is desired to keep them as erected as possible.