The earliest time of a reference to the name Sunda being used to identify a kingdom, is written on the Prasasti Kebon Kopi II stone inscription of 458 Saka (536 AD) and copperplate letters of the fifteenth century with royal instructions telling the existence of the Sunda kingdom. Another reference to the kingdom is the Sanghiyang Tapak inscriptions. There are also certain Chinese sources concerning the Sunda kingdom; the first source is a report from Chu-fan-chi from 1225 AD and the second source is the Chinese book ""shun-feng hsiang-sung"" from about 1430 AD. European explorers also report the existence of the Sunda kingdom. One of the explorers was Tomé Pires from Portugal. Tomé Pires, in his report “Summa Oriental (1513–1515)”, wrote about his journey to the Sunda kingdom. Diogo do Couto also wrote that the Sunda kingdom is thriving and abundant; it lies between Java and Sumatra, having between it and the latter the Straits of Sunda. Besides that, the Portuguese made a peace treaty with the Sunda kingdom in 1522 AD. This treaty is better known as the Luso Sundanese Treaty of Sunda Kalapa. Henrique Leme erected a padrão to memorialize the treaty.