Here is the discussion:
Here is another link:
One more link listing the items in Tamil itself:
There are many other sites, where this saying is analyzed differently by Tamilians.
Here are Indus Ladies, linking 16 prayers from Devimahatma to 16 number in the traditional benediction:
One more relating the number to the संकल्प in general for any Vedic rite, whether Grihya, Shrauta, or Smarta karma, in general, and also used as general blessings by Purohits:
शुभे शोभने मुहूर्ते आद्यब्रह्मणः द्वितीयपरार्धे
श्वेत वराहकल्पे वैवस्वत मन्वंतरे कलियुगे
प्रथमपादे जंबू द्वीपे भारतवर्षे भरतखण्डे
अस्मिन् वर्तमाने व्यवहारिक ------नामेन संवत्सरे
------अयने ------ऋतौ ------मासे
------पक्षे अस्यां ------वासरौ शुभनक्षत्र
शुभयोग शुभकरण एवंगुण विशेषण विशिष्टायां
शुभतिथौ श्री परमेश्वर प्रीत्यर्थं मम क्षेमस्थैर्य
विजयायुरारोग्यैश्वर्यापि वृद्ध्यर्थं धर्मार्थ
काममोक्ष चतुर्विध फलपुरुषार्थ सिद्ध्यर्थं
इष्ट काम्यार्थ सिद्ध्यर्थं मम समस्त दुरितोप
शान्त्यर्थं समस्त मङ्गळ वाप्त्यर्थं वर्षे वर्षे
प्रयुक्त श्री केदारेश्वर देवतामुक्तिस्य श्री
केदारेश्वर देवता प्रीत्यर्थं संभविता नियमेन
संभविता प्रकारेण संभवत्भि द्रव्यैः संभवत्भि
रुपचारैश्च कल्पोक्त प्रकरणे यावच्चक्त्य
ध्यानावाहनादि षोडचोपचार पूजां करिष्ये।
making it conform to 16 number.
Here is another list of 16:
and you can find many more varying lists making the total number 16. Now here is one more twist:
I don't think this is correct to relate it with wealth. As informed in the last page, the meaning might not have been twisted:
but a plain fact: Mathematical calculation bring out अष्टलक्ष्मी-s + अष्टसिद्धि = would also make the number 16. But is it needed?
It is not Vivek who has twisted the blessing, but people with Sanskrit knowledge. Here is the original wish of the parents:
एष्टव्या बहवः पुत्रा यद्येकोऽपि गयां व्रजेत् । यजेत वाश्वमेधेन नीलं वा वृषमुत्सृजेत् ॥ ८५.७१ ||
It is natural that many पुत्रपौत्राभिवृद्धि would naturally endows the prosperity unlike now a days, which prompted to comment:
"pathu pathinaru petru, pallandu platforathil vazhga"
But it is the original wish, so that any one of the sons will go and get Gaya, and have his PinDa to his pitR-varga.
But the number is insignificant, only idiomatic usage in Tamil equal to many. Is there any need to strive to relate it to Sanskrit to make the number 16 as Aishvarya (which is purely guessed on the verbal form "petru" as done in this site:
Many more discussions could be found on the net. Anyhow, I leave it to the Sanskrit scholars from Tamil Tradition to decide on it and fix the number to any source in Sanskrit Literature.