al-Da'iratu-l Fath of Shaykh Abu-l 'Abbas al-Mursi
There are certainly elements and perspectives of Tasawwuf that are analogous to Tantra but this is quite different than an incorporation of Tantra into Tasawwuf. Concrete examples can include awrad, dawa'ir, and lata'if, which correlate to mantras, yantras, and chakras, and a shared perspective concerning the theophanic quality of nature. Despite the formal and practical similarities of these elements, the content differs considerably because the manifestation is delimited in each case by the scope of the revelation. In Islam, every element of tasawwuf either derives from or is reconciled to the Quran. Likewise, the function and authority of the Shaykh is modeled after the Prophet Muhammad - may peace and blessings be upon him - and derived from the transmission of his initiatic and legislative power in contradistinction to a Shaivite Guru for example who is modeled after and derives his authority from Dakshinamurthi or Shiva in the form of the first Guru.
This is what I was referring to previously by stating that the classical Sufi tradition seems to avoid many of the problems of occultism, which is characterized by syncretism and eclecticism. There is no place for improvisations within the spiritual life because the recognition of the Quran as al-furqan, the criterion, is still very strong. I have encountered the teaching for instance that when the gnostic receives an inspiration, he measures it according to the criteria of the Quran and Sunna and if he finds it contradictory to the revelation he discards it. Bearing in mind that the Quran is a vast ocean of knowledge with a universalist perspective, this should in no wise be considered a diminution or exclusivism as much as a divinely established boundary preventing one from straying off the path.
Schuon asserts that "between one esoterism and another there are possibilities of mutual influence that can hardly exist on the exoteric plane, but in certain cases extend into the domain of outward forms." I believe that the converse also holds true, that between one exoterism and another there are divinely ordained formal limits which can hardly exist on the esoteric plane, but in certain cases extend into the domain of spiritual realization.