60 C is 140 F.
In general, it's not easy to find thermal design limits for phone SoCs. Thermal design limits on PC CPUs are pretty vague, Intel CPUs are notorious for having incomprehensible ones. The Ivy Bridge Core i7s have a Tcase of 67 C, and if you know a bit about Intel OCing you know that this number is frequently worthless for knowing how hot it's safe for a CPU to get. However the phone SoCs have a bit a wrinkle there, they aren't attached to huge heatsinks and fans blowing off cool air like PC CPUs, and the owner of the PC isn't basically holding the CPU in his bare hands.
In practice, there's no way to know if you are physically damaging your phone's CPU until you've actually cooked it. The SoC will THERMTRIP long before that happens and your phone will just freeze and you'll have to pull the battery. I used to do this to my old Droid X, that sucker could hit 1.5 ghz for the lulz but I would run Stability Test for about 3 minutes and the phone got so hot I couldn't touch it and then crashed.
The realistic scenario with a phone is, how hot does the phone get before you can't hold it without scalding yourself? The N4 hit 60 C (140 F) in that test. For reference, water boils at 100 C (212 F). Now I don't care much if the Core i7 in my gaming PC hits 60 C, but I'm not holding the CPU in the palm of my hand. It's different for phones from a simple practicality standpoint, even if the phone SoC isn't physically hot enough to self-immolate, it would be uncomfortable to try and hold. I don't particularly relish the idea of holding something thats 60 C in my hand, it sounds a bit painful. That's probably what drives phone designers in terms of what they will set the thermal throttle to.
dont have a mobile phone right now.
