Unfortunately, this quest is broken as it never begins as intended.
Rundi was one of the apprentices that Phinis Gestor speaks of when asked about missing apprentices. He does not, however, actually give the Dragonborn a quest to locate the apprentices.
According to Phinis Gestor, Rundi and his brother Borvir were researching ways to keep mead chilled.
Rundi's frozen corpse can be found at the unmarked Rundi's Altar location, northwest of Journeyman's Nook and southeast of Winterhold.
His weapon, Rundi's Dagger can be found there, as well as a Staff of Ice Spikes and an Alchemy skill book. Frost rune traps surround the area.
This quest is broken, as the logbook is not updated upon speaking to Phinis Gestor and no further dialogue can be had with him about the apprentices.