Fraction: a half vs one half; a third vs one third; a fourth vs one fourth

[Nessie]

1/ 1/2 can be read "a half" or "one half".
1/3 can be read "a third" or "one third"
so can 1/4 be read "a fourth" or "one fourth"?

2/ Despite its antiquity, certain aspects of its construction make it one of the truly wonders of the world

=> I don't understand why they use truly (an adverb) here. Is the sentence wrong?
_________________
... something we never have again, I know... I guess I really really know..

Sorry seems to be the hardest word...

[Yankee]

Hi Nessie

1. Yes

2. No, that word order doesn't work. However, if you moved the word truly as follows, it would be OK:
"Despite its antiquity, certain aspects of its construction make it truly one of the wonders of the world."
.