The earliest known signature of revolutionary astronomer Galileo Galilei is up for auction at Nate D Sanders this month.

The auction house claims that this extraordinary piece is one of just four surviving specimens of Galileo’s handwriting.

Galileo was tried for heresy in 1633 after arguing that the Earth revolved around the Sun

It dates to April 13, 1595 and acknowledges receipt of repayment of a debt from a friend.

It reads: "On the 13th day of April 1595, I, Galileo Galilei have received from the above mentioned Mr. Luigi forty scudi of seven lire."

Above this Luigi has written: "On the fifteenth day of March 1595 in Padua by the present writing, I, Luigi de la court, name myself true and legitimate debtor of Signor Galileo Galilei, mathematician for one hundred three scudi four lire, for the account which I owe him for the payment of the room and board that he has consigned to me and my servant by past promises and sworn oaths which oblige me to pay for all his good and tranquillity and in reliance on the truth written and undersigned. The present is valid as of my own hand." 

At the time Galileo was teaching mathematics at the University of Padua.

It was during his tenure here that he made many of his most important discoveries in fundamental and applied science.

The lot is offered with a minimum bid of $1m. 

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