The Prophet ﷺ prayed on a sheet of cloth put on by one of his wives who was menstruating. He was praying while (a part of) it was upon him.  

أَنَّ النَّبِيَّ ﷺ صَلَّى وَعَلَيْهِ مِرْطٌ وَعَلَى بَعْضِ أَزْوَاجِهِ مِنْهُ وَهِيَ حَائِضٌ وَهُوَ يُصَلِّي وَهُوَ عَلَيْهِ  

The Messenger of Allah ﷺ would pray at night while I lay by his side during my menstrual period. A sheet of cloth would be partly on me and partly on him.  

كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي بِاللَّيْلِ وَأَنَا إِلَى جَنْبِهِ وَأَنَا حَائِضٌ وَعَلَىَّ مِرْطٌ لِي وَعَلَيْهِ بَعْضُهُ