Reference: al-Hifth – Ahammiyyatuhu, ‘Ajaa.ibuhu, Tareeqatuhu, Asbaabuhu – Page 19
al-Badar at-Taali’ – Volume 1, Page 70
Jamaal ad-Deen as-Sarmadee said:
From amongst the most amazing of those who memorised [knowledge] in our time was Ibn Taymiyyah; He would read a book only once and it would be etched in his mind (i.e. he would have memorised it).