ABSTRACT This comparative case study takes up the examples of two Twelver lettrists, who together became two of the most important occultist authorities of the high Safavid period: al-Ḥāfiẓ Rajab al-Bursī (d. after 1410) and Maḥmūd Dihdār Shīrāzī (fl. 1576). Their projects are intimately connected, and can only be historiographically explained in tandem. Yet the first has been celebrated in the literature as a passionate, semi-extremist Twelver mystic, and the second—a sober, experimentalist Twelver occult scientist—totally elided. Nor has any study to date identified both authors’ primary point of scholarly reference: the New Brethren of Purity network of imperial Timurid and Ottoman Pythagoreanizing occultists radiating from late Mamluk Cairo, capital of the lettrist renaissance to which they were consciously heir. To correct such elisions and imbalances, we must forswear the persistent scientistic-cum-religionist dogma that vanishes lettrism and other mainstream occult sciences into the wastebasket, apolitical category that is ‘mysticism,’ thus exiling much of Safavid intellection from early modern history of philosophy, of science and of empire. For al-Bursī, taking a page from his contemporaries the New Brethren, is the first Shiʿi author to draw directly on Ibn ʿArabī (d. 1240) and Aḥmad al-Būnī (d. btw. 1225–33) both, the two foremost Sunni lettrists of the later Islamicate scholarly tradition, representing lettrist theory and lettrist praxis respectively; and Dihdār—the most prolific Persian author on practical Būnian lettrism of the sixteenth century, and hence immediate inspiration for the al-Bursī cult of the next—provides us an invaluable window onto how Safavid philosophy was actually imperially, occult-scientifically practiced, as well as the evolution of the Western grimoire tradition as a whole.