The Dangers of an Extended Meditation Session

It is not about the Physical dimension.

Suppose if you do not have physical body, what is the problem in sitting for 10,000 years, vedic rishi's were able to remain in samadhi for 300 years.

In Deep meditation you are separated from your physical body (which is not you)

Try to think that way.

I believe it's more of a legal disclaimer, or due to ignorance.

I have met monks who sat straight for days (2 to 3 days) under recommendation of their teacher - this is in the Chan lineage. In Chan, you get all sorts of affliction and pain but if you don't quit and be vigorous, you will progress quite fast. It is said long sitting produces Chan. You have to be patient.

If by any means you get stuck in a state, your Master should be able to spot that and help you.

Please see Master Hsuan Hua's texts, it has some reports of monks sitting days straight in samadhi.

It is unlikely Gotama/The Buddha sat for 49 days in a single sitting as the legendary stories claim. For example, the Maha-Saccaka Sutta explains how Gotama nearly died due to not eating food and his enlightenment only occurred after eating food.

...that pleasure that has nothing to do with sensuality, nothing to do with unskillful mental qualities...is not easy to achieve with a body so extremely emaciated...Suppose I were to take some solid food: some rice & porridge.' So I took some solid food: some rice & porridge. ...So when I had taken solid food and regained strength, then — quite secluded from sensuality, secluded from unskillful mental qualities, I entered & remained in the first jhana:

It is doubtful, after nearly dying, that only one meal would sustain Gotama for another 49 days.

The Udana states, for 7 days after enlightenment: "at the foot of the Bodhi Tree, having just realized full enlightenment, the Lord sat cross-legged for seven days experiencing the bliss of liberation". A 7 day single sitting of a fully enlightened Buddha may be possible & is not as unlikely as 49 day sitting of an unenlightened Bodhisatta (seeker of enlightenment).

When considering for the rest of his life the Buddha generally ate one meal per day, the stories or fables about a 49 day single sitting appear exaggerated, similar the the 40 days & 40 nights of Jesus in the desert.

According to Empty Cloud The Autobiography of Master Xu Yun (famed Chinese monk of the 20th century usually with name transcribed as Hsu Yun).

One day I cooked taro in a cauldron and sat cross-legged while waiting for my meal to cook and involuntarily entered the state of samadhi.

MY 63RD YEAR (1902/03)

Master Fu-cheng and others who stayed in nearby huts were surprised that I had not called on them for a long time and came to my hut to present their New Year greetings. Outside my hut, they saw tigers’ tracks everywhere with no traces of man. They entered my hut and seeing that I was in samadhi, they awoke me with a qing (a musical instrument made of stone, the sound of which is subtle but penetrating). When I returned to self-consciousness, they asked me, ‘Have you taken your meal?’ I replied, ‘Not yet, the taro in the cauldron should be well cooked by now.’ When its cover was lifted, the cauldron was covered with an inch of mould. Fu-cheng was startled and said, ‘You must have been in samadhi for half a month.’ We then melted ice, cooked taro and ate our fill. They joked with me and left.

Now you can take this story with a grain of salt, but I wouldn't discount the possibility of hibernation-like state for deep meditation...

From a physiological point of view, the body is not designed to remain fixed and stationary for long periods. After two hours there is a risk of blood clots. This can be ameliorated by doing a period of walking meditation every two hours. Such practices are also bad for the lymphatic system, which is probably why diet has been emphasized by many yogins, to reduce toxicity in the body. On the other hand, the great Korean master Seongcheol (1912-1993) is reputed to have remained seated inside a very small area (too small to lie down in) for eight years without sleeping. A fellow monastic who disbelieved that Seongcheol was actually doing this spied on him, verified that he was in fact doing it, and tried it himself; his teeth fell out! From a psychological point of view, there is some evidence that there is about a 10% chance of precipitating a latent psychosis as a result of fairly short periods of meditation retreat. In one case I read about, after two days a female experienced a psychotic break which required ten years of psychiatric treatment to rectify. So meditation is not something to be undertaken casually. It is a serious spiritual quest no different from the shamanic quest. We have an idea that it's just a relaxation exercise. This is grossly naive. There are cases where people in the West have died as a result of extreme Buddhist practices. What is your reference to the Buddha sitting in meditation for forty days and forty nights? According to the Pali Canon, the Buddha remained sitting in meditation for seven days and nights after attaining nirvana. My fellow Torontonian Tim Ward wrote a book called What the Buddha Never Taught in which he discusses "samadhi suicde," a Theravadin ascetic practice in which one intentionally meditates oneself to death. Of course, such a person immediately ceases to be a member of the sangha for violating the first precept (third defeat or parajika offence) against killing. Anyone who advocates such practices is also automatically banned. The Buddha forbade such practices after discovering an outbreak of suicide amongst the monastics while the Buddha was on retreat.