Shoola Yoga has been used in different contexts in the Hindu astronomical and astrological works. In the astronomical sense, it is one of the 27 yogas which are related to the apparent motion of the sun and the moon. The 27 yogas are formed, and Shoola or Sula is the ninth in the order.
Sarpa (serpent) is the lord of this yoga, and it is considered inauspicious, particularly its first five ghatis (two hours). According to Hora Ratnam, a compendium of several astrological texts, persons born under this yoga are fortunate, possess good qualities but have to suffer from sula (pains) in the body, particularly in the stomach.
According to Mansagari, such a person will also be religious minded and expert in getting education and acquiring wealth. According to Jataka Parijata, if in the horoscope of a person, all the planets, excluding Rahu and Ketu, occupy any three signs, then Shula Yoga is formed. Such a person would have an angry and quarrelling temperament and though with a keen interest in acquiring money, would be poor. He would be brave and his body would bear signs of wounds.
These views are supported by other astrological texts like Mansagari. Brihat Parasara-hora sastra also defines Sula Rahi. It is stronger of the two sings, which are eight from the ascendant, and the eight from the seventh house, i.e., second from the ascendant. This is used to decide the order of dasa (periods) of the signs in a horoscope.
There is also a varasula. For each day of the week, travel is proscribed in a particular sula (direction).
Monday and Saturday – east
Tuesday and Wednesday – north
Sunday and Friday – west
Thursday – South.