Institute of Vedic Astrology situated in Indore, in state of Madhya Pradesh in India has suggested these concepts in online Vaastu Shastra courses.
For this test make a dry hollow which is level at the base and all sides.
Now take four Earthen lamps. Fill the lamps with oil (ghee) and cotton thread. Now keep this four lamps on four directions of the site. Now absence which lamp burns for longest time.
If lamp on East direction burns the most then it is very good land for Brahmins, if the lamp burns longer in the West, South and North, then this land is good for Vaishyas, Kshatriyas and Shudras respectively. This test shows the radiation which are auspicious for a particular strature of people.
Colour Radiation Test:
Take four coloured flowers i.e. white, red, yellow and black. In evening time, place them in the day in the order of black in North direction, yellow in West, red in South and white in East. In the morning come and observe these flowers. If the white flower blooms and doesn’t become dry, then this soil has good radiations for Brahmins. Similarly, if other flowers like yellow bloom and all others dry up, then this land is suitable for Vaishya. Similarly red flower for Kshatriya and black for Shudra. This test shows the colour radiation, which fall on the land and based on the colour radiation one can access which strature of people will benefit the most out of it.