THe problem with asking this question is that different practices have radically different definitions of "transcendent."

The TM definition is found in this research and theory review paper published in the special issue on meditation research of the Annals of the New York Academy of Sciences:

• Transcendental experiences during meditation practice.

  "The subject/object relationship during transcendental experiences is characterized by the absence of time, space, and body sense—the framework that gives meaning to waking experiences. "

Though that is an oversimplication that the author did for scientists who are not familiar with the concept.

A more detailed description is found in the body of the paper:

• • The state of Being is one of pure consciousness, completely out of the field of relativity; there is no world of the senses or of objects, no trace of sensory activity, no trace of mental activity. There is no trinity of thinker, thinking process and thought, doer, process of doing and action; experiencer, process of experiencing and ob- ject of experience. The state of transcendental Unity of life, or pure consciousness, is completely free from all trace of duality. -Maharishi Mahesh Yogi

  The experience of pure consciousness is called Transcendental Consciousness. In this state, one has transcended the subject/object dichotomy that marks waking experiences; the subject—self- awareness—is both the subject and object of ex- perience. It is a Self-referral experience. On one hand you can say there is no content in pure con- sciousness. On the other, you could say the content is wakefulness itself23 or consciousness itself.24 In the Vedic tradition, Transcendental Consciousness is called “the fourth” or turiya chetana.

  Transcendental Consciousness occurs spontaneously during TM practice. One starts the mantra, and then the process unfolds in its own time. There may be momentary experiences of Transcendental Consciousness during a meditation session, or these experiences may last from 10 to 40 s in duration.

Note that technically speaking, "transcendental experience" is an oxymoron.

The genuine "transcendental" state is characterized in the Yoga Sutra as the complete absence of any "object of attention," and it is thought to emerge when the mechanism by which awareness exists in the brain — activity of the thalamus that mediates sensory input and thalamocortical feedback loop projects to the cortex — has shut down as it does during non-REM sleep even though the part of the thalamus that facilitates long-distance communication between cortical regions continues to operate as it does during waking and dreaming. As a side-effect of this abrupt change in thalamic functioning, many people appear to stop breathing for the duration.

.

Fred Travis, the researcher who wrote teh above paper, has published quite a few studies on the transcendental state and he is in charge, world-wide, of research on TM.

These are some of the papers that have been published on this awareness cessation state during TM:

• Breath Suspension During the Transcendental Meditation Technique

• Electrophysiologic characteristics of respiratory suspension periods occurring during the practice of the Transcendental Meditation Program.

• Metabolic rate, respiratory exchange ratio, and apneas during meditation.

• Autonomic patterns during respiratory suspensions: possible markers of Transcendental Consciousness.

• Autonomic and EEG patterns distinguish transcending from other experiences during Transcendental Meditation practice.

And you might want to familiarize yourself with the research before you interview people (TMers) whose definitions of such terms are radically different than what you will find when dealing with practitioners of other meditation practices.

.

Fred's email and other contact info can be found on his faculty webpage:

https://www.miu.edu/academic-departments/maharishi-vedic-science/faculty/gallery/fred-travis

.

Good luck.