Giordano Vitale

As an adolescent he left (or was forced to leave) his city and, after an adventurous youth (that included killing his brother-in-law for calling him lazy) he became a soldier in the Pontifical army.

In Rome he made acquaintance with the renowned mathematicians Giovanni Borelli and Michelangelo Ricci, who became his friends.

He was employed for a year as a mathematician by ex-Queen Christina of Sweden during her final stay in Rome.

Giordano died on November 3, 1711, and was buried in the San Lorenzo in Damaso basilica church in Rome.

[1][2] So using a figure he found in Clavius, now called a Saccheri quadrilateral, Giordano tried to come up with his own proof of the assumption, in the course of which he proved: The interesting bit is the second part (the first part had already been proved by Omar Khayyám in the 11th century), which can be restated as: Which is the first real advance in understanding the parallel postulate in 600 years.