Kumbha (कुम्भ) is usually translated as pot. The comparisons with other Indian philosophies, however, show that the term mostly has only a symbolic meaning and the actual meaning is something else.
For example: Shilpashastra (iconography): Kumbha (कुम्भ, ‘pot’) is a weapon (āyudha or bādhra) according to the Vāstusūtra Upaniṣad.
Vastushastra (architecture): Kumbha (कुम्भ) refers to classification of a temple/buidling (prāsāda), according to Samarāṅgaṇasūtradhāra chapter 63.
Vaishnavism (Vaishava dharma) Kumbha (कुम्भ) corresponds to “aquarius” (mid February to mid March) and refers to one of the zodiac signs (rāśī) in the Vedic calendar.
The term kumbha (Sanskrit: कुम्भ) refers in yoga and tantra to the process of inhaling air into the area of the navel and staying there for a while while imagining that the breath is in a kind of pot. Kumbhaka (Sanskrit: कुम्भक kumbhaka m. u. n.) means holding the breath in the navel area while practicing Pranayama breathing.
In the Pali suttas, there are several places where kumbha as well as kumbhaka are mentioned, but the connection to this breathing technique was never made there, because this knowledge was only passed down orally in the past.
I think that in some parts of the Pali canon the terms kumbha and kumbhaka have now been translated incorrectly, and that instead of the previous facts, the texts actually contain descriptions of body and breathing exercises, and that the historical Buddha also practiced various body and breathing exercises.
There is also some buddhist yogic and medicine systems in Thailand called Nuad Thai or Nuad Boran, that it originated in India around the lifetime of the Buddha (aka Siddhārtha Gautama or Buddha Shakyamuni). The founder (or inventor) of this Thai Massage and healing system is thought to have been an Indian doctor from Northern India known as Dr. Jivaka Kumar Bhacchal (aka Dr. Shivago or Shivago Komarpaj), a contemporary of the Buddha and the personal physician of the Indian King Bimbisara.
Thai Massage Origin | History of Massage in Thailand
In this yoga and massage system, there are also different body and breathing exercises, and if Buddha’s personal doctor knew these methods and techniques, then Buddha should also have known and taught these things.
In the Boran Kammatthana, Yogavacara texts, as well as in the Buddhist yoga manual that was found during the Turfan expedition, there are also other methods and techniques than those taught in modern Theravada, which for me is a clue that the historical Buddha taught more methods and techniques than are attributed to him today.