Stardust has given his views on your questions. But I\'m trying to add what I know with that.
1. We shouldn\'t sleep in the North-South direction as there is a big bar magnet under the earth and it\'ll affect our mind. This is our first standard science and everyone will be knowing that and hence there is no need for any reasoning. But South-North direction is good for medical treatments. In few cases if the patient is asked to lie in the South-North direction, the treatments will be successful.
But generally for sleeping, West-East is better, i.e. you should keep your head in the West direction and face East direction. Coz always West direction is higher than the East direction of the Earth. Everyone knows that Earth is rotating itself clockwise and is revolving around Sun. Earth\'s full rotation is a day and it\'s full revolution a year. Even this is also a basic science. But Earth is not standing straight while rotation. It\'s always tilted (slanted) 23.5 degrees towards the East. Hence West is always higher than the East.
2. Regarding dhisti, if you can understand the concept of \'aura\' it\'ll be easy to understand. \'Aura\' is an invisible energy shield (like border) around every thing(both living & non-living beings). All these dhisti and other negative things will first come and deposit in our aura and then it\'ll start affecting us slowly. Salt, Red Chilli and Fire have the power to remove negative energy. Hence to remove negative energy (dhisti) from our aura, people will use Salt, Red Chilli and Camphor. This is definitely true and it\'ll work.
3. For this, the answer for your first question itself would\'ve given the answer. Coz of Earth\'s position and rotation, Cosmic Energy will be entering the Earth thru North-East direction and hence it is the most auspicious direction in Vaastu. It is called as \"Eshanyam\" and they\'ll say that Easwar(God) is residing in this direction and we\'ll get his energy from this direction. Coz of this, Cosmic Energy will be flowing well in the North and East sides. Hence it is asked to face any one of these directions, while meditating.
These are the scientific and real reasonings behind this. But religiously, Earth symbolizes \"Sun\" and North symbolizes \"Kubera\". You know why people are worshiping these two Devas. Kubera is ruled by Lakshmi and hence we\'ll get wealth. Surya Namaskar is a very ancient thing and various traditions and cultures also have been practicing the worship of Sun. It\'s for Health.
Hope I\'ve solved your doubt to a certain level. If you have any other doubts, feel free to write us.
All the Best!!!
Not sure if I am posting in the right forum.
I have three questions:
1. It is said Sleeping with your head in a particular direction produces certain effect. Can some one tell me what direction produces what effect. Even better if the logic behind it is explained (like flow of prana, energy etc).
2. We have this tradition of taking \'dhisti\' (telugu word), by taking a handful of salt and rotating it around the person to ward of bad effects. Can someone explain the logic behind it again? Why only salt is used, does it have some special properties? And does it really work?
3. Why usually all books mention meditation should be done facing north or east ?