It is narrated from Sayyidah Umm al-Hasan (may Allah be pleased with her): I saw Sayyidah Umm Salamah (may Allah be pleased with her), the honoured wife of the Prophet (peace and blessings be upon him), prostrating on a leather cushion because of an eye inflammation (ophthalmia) she had.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3674
It is narrated from Sayyidah Umm al-Hasan (may Allah be pleased with her) that she saw the Mother of the Believers, Sayyidah Umm Salamah (may Allah be pleased with her), praying on a pillow because of an ailment in her eyes.
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that he gave a concession regarding prostrating on a pillow and a cushion.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3675
Abu Ishaq (may Allah have mercy on him) relates: I saw Sayyiduna Adi bin Hatim (may Allah be pleased with him) prostrating on a wall in the mosque whose height was about one cubit.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3676
Mijza'ah bin Zahir (may Allah have mercy on him) narrates from a man among the People of the Tree whose name was Sayyiduna Uhban bin Aws (may Allah be pleased with him): he felt pain in his knees, so when he prostrated he would place a pillow under his knees.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3677