"perfect 10"

[plop1389]

Where does this saying come from? The perfect 10 what?

[Ouisch]

As a rule, a generic way of rating something is on a scale of one to 10.  For example, a doctor might ask you, when you have a bad headache, "on a scale of one to 10, how bad is the pain?"  Perhaps you're comparing a meal in one restaurant to another - for emphasis, you'd say "Joe's Place was good, I'd give it an 8, but Runyon's Beanery was even better - almost a 10!"  Ten is usually the superlative, whether it's the most, the best, the worst.  So if someone is a perfect 10, they're the ultimate, the maximum.

[tashatz]

Could be reference to mathematician Emil Borel:

...Mathematicians generally agree that, statistically, any odds beyond 1 in 1050 have a zero probability of ever happening.... This is Borel's law in action which was derived by mathematician Emil Borel....

OR...

 

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value

[jno]

performers - dancers or gymnasts, for instance - are often marked out of ten.

[Clanad]

Additionally, a movie made in 1979 starred Bo Derek and Dudley Moore which was titled "10"... indicating the quality of Bo Derek's character's appeal, etc...

[Trillipse]

it's an old camping phrase, "the perfect tent"