I'm looking to find out what the Latin for "from the heights" is, as the equivalent of Oscar Wilde's title "De Profundis".
How about de excelsis (cf. the phrase gloria in excelsis Deo)?
From Oxford Latin Dictionary:
excelsum ~ī, n.
1 High ground, an eminence, height. b a high altitude; (also pl.).
2 Loftiness (of rank, station, etc.), high position.
I think the most fitting antonym for de profundis is de caelis (alternatively spelled de coelis). Literally, this means "from the heavens" or "from the skies".
Take a look at what caelum can mean. I used it in the plural. The best choice of words depends on your exact context, of course.