who systematized the classic Theravāda meditation, dividing them into samatha and vipassana types and listing 40 different forms (known as "kammaṭṭhānas", "workplaces") in his magnum opus, the Visuddhimagga.Crosby, Kate (2013), Theravada Buddhism: Continuity, Diversity, and Identity, John Wiley & Sons, p. 141. This text has remained central for the study and practice of Theravāda meditation. Buddhaghosa's commentary on the Satipatthana sutta ("Bases of mindfulness discourse"), as well as the source text itself, are also another important source for meditation in this tradition. Buddhaghosa's work drew heavily on the Pali suttas as well as the Pali Abhidhamma. Kate Crosby notes that Buddhaghosa's work also "explicitly refers to the contemporaneous existence of secret meditation manuals but not to their content." Regarding post Visuddhimagga Theravāda meditation, according to Kate Crosby, In the period between the Visuddhimagga and the present, there have been numerous meditation texts, both manuals and descriptive treatises. Many of the texts found in manuscript collections relate to meditation, some on a single, simple subject such as the recollection of the qualities of the Buddha, others more complex. Little research has been done to assess their variety. One difficulty is that meditation manuals as such are often in a mixture of a classical language, that is, Pali, and a vernacular that may or may not be a currently used language. Also, actual manuals often contain prompts or reminders rather than an in-depth explanation. In recent years it has emerged that there is still extant a relatively high number of manuals and related texts pertaining to a system of meditation called – among other things – borān kammaṭṭhāna or yogāvacara. Its core text, the Mūla-kammaṭṭhāna "original, fundamental or basic meditation practice," circulated under a number of different titles, or without a title, throughout the Tai–Lao–Khmer and Sri Lankan Buddhist worlds. Some versions of this text are simple lists of kammaṭṭhāna and from that perspective look entirely in accord with the Visuddhimagga or Theravada Abhidhamma texts. Other versions contain extensive narratives, explanations of symbolism, and of the somatic locations involved in the practice that make it clear that we are dealing with techniques of practice not described in the Canon or Visuddhimagga.According to Crosby, the esoteric borān kammaṭṭhāna or yogāvacara meditation tradition was the dominant form of meditation in the Theravāda world during the 18th century, and may date as far back as the 16th century. Crosby notes that this tradition of meditation