Cornelius’s recommendation sent Horkheimer to Husserl where he met Heidegger

Evidence

Cornelius sent Horkheimer, with a letter of recommendation, to study with Husserl in Freiburg for two semesters, and Horkheimer was deeply impressed when he met Husserl’s assistant, Martin Heidegger. — Rolf Wiggershaus, The Frankfurt School, 176