In his Tafsir named "an-Nahrul-Madd", the Grammarian Abu Hayyan al-'Andalusi reported about Ibn Taymiyah having this belief.
He said:
In his handwriting, a book of Ahmad Ibn Taymiyah, who was contemporary with us, which he called "Kitab-ul-‘Arsh", I read: Allah sits on al-Kursi and has left a space for the Messenger of Allah to sit with Him. At-Taj Muhammad Ibn ‘Ali Ibn ‘Abdil-Haqq al-Baranbari pretended that he is a promoter of his ideas and tricked him, until he took it from him; we read that in it.
[The author of "Kashf-uz-Zunun" reported that about him also in Volume 2, page 1438.]
This reporting of Abu Hayyan was omitted from the old printed copy. However, the manuscript confirms it.
In his commentary on "as-Sayf-us-Saqil", page 85, Az-Zahid al-Kawthari said explaining the reason of omitting these statements of Ibn Taymiyah:
The editor of as-Sa‘adah Printing House told me that he found it very ugly and he omitted it upon printing so that the enemies of al-'Islam would not use it. Then he requested that I record that here to catch up what he missed and out of sincerity to the Muslims.
