origin of the number "e"

[emre]

Hi, mathematicians. In the following link, there are Euler's articles and books coded as E1, E2, E3,.... I wonder in which article he introduces his special number which we now know as the number "e".

 

http://www.math.dartmouth.edu/~euler/

[the tree]

The Wikipedia article covers the history of 'e', the constant has been in use since before Euler - which is often the case, see Stigler's law.