Zhang Xu of Tang Dynasty wrote "Heart Sutra" 

Zhang Xu's "Heart Sutra in Cursive Script" was first seen in "Outstanding Stele Inscriptions", and Zhang Xu was written under the title of "Heart Sutra in Tangcao". Previously, in the Forest of Steles, there was "Heart Sutra in Cursive Script" moved from Baita Temple by Sun Ren, the prefect of Chenghua Period in the Ming Dynasty. "Guanzhong Epigraphy and Stone Text Cunyi Kao" records both the "Heart Sutra" in cursive script, and the "Heart Sutra, Tie Pain Tie, Qian Wen Duan Stele" note "all Zhang Xu cursive script, no date", and said "the three stones on the right are all "In Xi'an Forest of Steles". Zhang Xu's "Heart Sutra in Cursive Script" was last seen in the "Forest of Steles List" in the third year of the Republic of China (1914), but its whereabouts have been unknown since then.