Narapatijayacarya 4.4.90

In the piercing of one's own, a friend's, a neutral's, and an enemy's [sign] in regions and so forth,
a malefic planet brings harm by one, two, three, and four quarters respectively.

On "vakroccagaḥ": A planet that is retrograde or in its exaltation possesses full strength. A planet in its own mansions, that is, in its own houses, possesses full strength. For the planets beginning with the Sun, the zodiacal signs Aries, Taurus, Capricorn, Virgo, Cancer, Pisces, and Libra are, in order, the places of highest exaltation rays; within them, the highest exaltation [degrees] are, in order: ten [for the Sun], three [for the Moon], twenty-eight [for Mars], fifteen [for Mercury], five [for Jupiter], twenty-seven [for Venus], and twenty [degrees for Saturn]. Beyond the point of highest exaltation, the seventh position by counting across half the zodiacal circle, with the very same fractional divisions (aṃśa), is the depression position. On "uccānnīcācca": The fourth position from the exaltation and from the depression, that is, from the exaltation place and from the depression place, is called the neutral position. When a planet is ahead of or behind that, that is, ahead of or behind the neutral position, its strength is to be determined by the rule of three. Now, some wish to determine the strength by the rule of three from a planet's position ahead of or behind its own sign; their opinion is not sound. When a planet is in its exaltation sign, it gives full strength; when a planet is situated in its depression sign, it gives half strength. Situated in its own domain, in its own house, it possesses full strength; in a friend's asterism, in a friend's zodiacal sign, its strength is diminished by a quarter. On "ardham": When situated in a neutral house, the strength is half. When situated in an enemy's house, that is, in an enemy's zodiacal sign, its strength is to be known as one quarter, a fourth part. In between, the strength is to be determined by the rule of three. On "evaṃ deśādināthāḥ": Thus, according to the aforementioned manner, those planets that are the lords of regions and so forth are positioned to pierce the pentad of phonemes and so on of a region through the left, frontal, and right astrological piercings. There, when an astrological piercing occurs, whether the planets causing the astrological piercing are friends, enemies, neutral, or indifferent to the lord of the region must be carefully considered. For example, if the ruler of a ritual circle is the Sun, and that ritual circle is pierced by the Moon, Jupiter, and Mars, then, because these are friends of the Sun, they bestow auspicious results in the manner to be stated below. On "svamitrasama-": In regions and so forth—in a region, in a ritual circle, and in commodities—it gives an auspicious result on the right side from an astrological piercing of one's own, a friend's, a neutral's, or an enemy's [entity]. By four, three, two, and one quarters: in an astrological piercing of one's own [entity] the result is full; in an astrological piercing of a friend's [entity] it is diminished by a quarter; in an astrological piercing of a neutral's [entity] it is half...