Green’s Dictionary of Slang

1. of a man, to enter a woman and commence intercourse [SE scale, to climb; thus synon. with mount v.¹ ].

1607		Middleton Widdow of Watling-streete I i: And I, whom never a man as yet hath scaled, [...] vow never to marry to sustain such loss.
1966		B. Jackson Get Your Ass in the Water (1974) 127: I said, ‘Who’, before I scale your rusty thighs and suck your bloodshot tits, / I’ll drink a gallon a rattlesnake blood and swim in a ocean of shit’.

2. to impress, to astonish [? SE phr. scale the heights].

1902

H. Baumann Londinismen (2nd edn).