1. BPHS Volume 1 chapter 20 and Sloka 13 give the combination as "the Sun should be in any of Trik Bhava(6,8 or 12) at the same time lord of 6th should be in 5th, lord of 8th in 9th and lord of 12th in ascendant.
2. While "Jaataka Parijat" states in volume one Chapter 13 and Sloka 63 that the Sun be placed in any of 'Dusthana' from natal ascendant or natal Moon at the same time the Sun or the Moon be placed in the Dawadamsha of Leo or Pisces.
[ A posthumous birth is a birth of a child after the death of a parent, mainly father in Indian culture.]
Case studies :
1) Vijayendra Vijay : 5-8-1991 3.45 PM, ooty,Tamilnadu.
Vijay Goel Thanks !
This chart sun is in dusthana, aspect by saturn in D1 & D9,
Leo rasi is in 7H in D12 as Khumbh lagna is rising, pisces is 10 min away ?.
We can see more chart to verify this classical source.
2) Vivek Padhye: There are other combinations also for posthumus child so we should also keep that in mind
The example I have may need some rectification
Date: November 28, 1956
Time Zone: 5:30:00 (East of GMT)
Place: 73 E 23' 00", 16 N 23' 00"
If the Ascendant is Virgo(10 minutes back) then sun is in 3H and Dwadasamsa is Of leo.But I am not perfect iin BTR.If you want I can give life events.
3) Bhagavathi Hariharan :this is a chart that was posted in my groups few years back, Oct10, 1967; 12.20PM; kuala lampur (7.30 east of GMT), malayasia. the native was born 10 days after father's death. This does not have the classic combination. The chart was posted on a different context. I tried to look for the combination of posthumus birth, but could not.