Reference: Tahtheeb al-Kamaal – Volume 32, Page 58
al-Kaashif – Volume 3, Page 273
al-Hifth – Ahammiyyatuhu, ‘Ajaa.ibuhu, Tareeqatuhu, Asbaabuhu – Page 25
None of our companions were better at memorising hadeeth than him (Yahyaa ibn Yamaan); He would memorise 500 hadeeth in a single sitting.