The tradition of hardstone carving had existed for a longtime in India and the Islamic courts of Iran and central Asia. The Taj Mahal walls display exquisitely carved floral sprays sculpted in shallow relief in white marble. The superb quality of the sculpted flowers on the mausoleum can be attributed to the ancient tradition of stone carving in India. Engravings in European herbal books that had been brought into India by foreign visitors inspired their naturalistic forms.
The calligraphy on the Taj was carefully selected and artistically inscribed in the Mosque and the tomb proper, in panels around the arched portals and in alcoves and niches. These are mostly verses of the Quran, the word of God as revealed to Muhammad.
Muslims constitute 11 percent of the population and are the largest religious minority. Many of these followers of the monotheistic faith of Islam are descendants of Middle East and Central Asians who began entering the subcontinent as early as the 8th century. Most, however, are descendants of converts from Hinduism and other faiths.
The lettering of the Quranic calligraphy on the Taj appears to be the same from top to bottom. This amazing optical illusion was created by Shah Jehan's calligraphers who gradually heightened the size of the letters as their distance from the eye increased. From the ground the dimensions seem to be the same at every point. This ingenious Trompe L'oeil (Trick of the Eye) effect is also used on the main gateway arch of the Taj.
Inside the Mosque are inscribed all fifteen verses of Surah 91, entitled 'Wa-Shams' (The Sun) and all four verses of Surah 112 entitled 'Surah Ikhlas' (The Purity of Faith).