Narada Purana (Jyotisha Selections) · by Vyasa
Chapter 2 · Signs, Planets, Birth
जातकम् १
शताब्दं गीष्पतौ कर्के कंटकस्थसितेज्ययोः ।लयेशेंगे शुभैर्हीनेऽष्टमे खाब्धिमितं वयः ॥ ११७ ॥
In the full Narada Purana (Purva Bhaga) this is chapter 55, verse 117.
That gives a hundred years. Jupiter may be in Cancer, with Venus and Jupiter in corner houses. The 8th lord may be in the lagna (rising sign), with no good planet in the 8th. Then the age is 40.
Simple meaning: Jupiter in Cancer with these placements gives forty years. Another rule gives a hundred.
लग्ने शेष्टमगेष्टेशे तनुस्थे पंचवत्सरम् ।
Lagna and 8th lords swapped may shorten life to five years. Another placement gives fifty.
एतद्योगजमायुः स्यादथ स्पष्टमुदीर्यते ।
The exact life is worked out with a method that follows the strongest of the Sun and Moon.
अंशायुः सबले लग्ने तत्साधनमथो शृणु ।
If the rising sign is strongest, the degree method is used. Full years for each planet are listed.