I am a yoga practioner and sanskrit enthusiast. I have been doing some work to collect the common prayers and shlokas - and I have also been contributing to wikipedia, for instance http://en.wikipedia.org/wiki/Mantra page.
Now, I have been looking for the source of the sarveshaam -prayer:
सर्वेषां स्वस्ति भवतु । सर्वेषां शान्तिर्भवतु ।
सर्वेषां पूर्नं भवतु । सर्वेषां मड्गलं भवतु ॥
Sarveṣāṁ Svastir Bhavatu
Sarveṣāṁ Śāntir Bhavatu
Sarveṣāṁ Pūrṇaṁ Bhavatu
Sarveṣāṁ Maṅgalaṁ Bhavatu
Often it is chanted with
Āsato mā sad gamaya, which comes from Bṛhadāraṇyaka Upaniṣad 1.3.28. But does Sarvesham come also from there?