another way to divide the practice of mahāmudrā is between the tantric mahāmudrā practices and the sutra practices. tantric mahāmudrā practices involves practicing deity yoga with a yidam as well as subtle body practices like the six yogas of naropa and can only be done after empowerment. after the preliminary practices, the kagyu school's sutra mahāmudrā practice is often divided into the ordinary or essential meditation practices and the extraordinary meditation practices. the ordinary practices are samatha (calming) and vipasyana (special insight). the extraordinary practices include "formless" practices like 'one taste yoga' and 'non-meditation'. the tradition also culminates with certain special enlightenment and post-enlightenment practices. according to reginald ray, the "formless" practices, also called "essence mahamudra," is when "one engages directly in practices of abandoning discursive thinking and resting the mind in the clear, luminous awareness that is mahamudra." the reason that preparatory practices and "form" practices like deity yoga and vipasyana are needed is because formless practices are quite difficult and subtle, and most practitioners are not able to enter into the simple essence of mind successfully without considerable mental preparation.