They are Anoushka's Ladder and the Way of the Locust. You need a high level of Coils just to be able to take the first dot in either Coil, and it's entirely up to the ST whether they exist or not by RAW (they're "apocryphal" and may or may not actually exist in any given chronicle). Anoushka's Ladder requires very high Humanity, as you already know. The Way of the Locust, on the other hand, will result in very low Humanity as it involves diablerizing humans.

Yummy, yummy human souls.