The Messenger of Allah ﷺ used to place his mount in front of him as a sutrah and pray facing it.
حدثنا معتمر عن عبيد الله عن نافع
أن رسول الله ﷺ كان يعرض على راحلته ويصلي إليها
Its chain of transmission is sahih. Muslim narrated it in 1:142 from Ahmad bin Hanbal with this same chain. Bukhari narrated it in 1:478-479 from Muhammad bin Abu Bakr Muqaddami from Mutamir, with the same chain."He turns his mount sideways" (yuridu ala rahilatihi), with the ra doubled, meaning he made it crosswise. The word "ala" here is an insertion found in both original sources, but it is not mentioned in the Sahihayn.