Sample letter of Blaise Pascal to his brother-in-law Florin Périer:

November 15, 1647

I am taking the liberty of interrupting you in your daily professional labors, and of bothering you with questions of physics, because I know that they provide rest and recreation for your moments of leisure... The question concerns the well-known experiment carried out with a tube containing mercury, first at the foot and then at the top of a mountain, and repeated several times on the same day, in order to ascertain whether the height of the column of mercury is the same or differs in the two cases... For it is certain that at the foot of the mountain the air is much heavier than at the top.

Blaise Pascal