A page from the astronomical treatise Sullam al-sama'
|Original title||سُلَم السَماء|
Sullam al-sama' also known as Resaleh-ye Kamaliyyeh (Arabic*: سُلَم السماء, Transliterated as Sǒllam os-Samā') meaning "The Ladder of the Sky" or "The Stairway of Heaven" is an astronomical treatise  written by the Persian mathematician and astronomer Jamshid Kashani in 1407 about the determination of distance and size of the heavenly bodies such as the Earth, the Moon and the Sun.
Kashani finished the writing of the book on 1 March 1407. He mentioned at the preface of another book of his, Meftah al-Hesab (lit. "The Key of Arithmetic") that: "I studied all books on astronomy that the scientists had written before me and i realized that they had many difficulties and disagreements about the determination of the size or distance of the astronomical objects like Mercury or Venus to the Sun. So I decided to write this book and I named it Sullam al-sama' to be a guide for the wise."
The book shares its title with a TV series about Kashani produced in Iran in 2008.