Specific location
To be more precise about the location, as this schematic is listed as being found in the Old Temple but the walkthrough of Ameridan's End omits it:
Climb the pile of rocks on the east/right side of the map near the door that requires the Deft Hands perk. There will also be an unlit torch for the Firestarter achievement in the same area.
A map has been posted (under a spoiler tag) here: http://forum.bioware.com/topic/551106-hakkons-wrath-schematic-jaws-of-hakkon/