Q:

Capital cursive E in math mode? 

How do I get a capital Cursive "E" in math mode?  See picture encl. 

A:

To assemble the suggestions in the comments, you can do the following:
Code
\documentclass{article}

\usepackage{mathrsfs} % https://www.ctan.org/pkg/mathrsfs

\begin{document}

\begin{equation}
  \mathscr{E} % uses `mathrsfs`
  \mathcal{E}
  \varepsilon
\end{equation}

\end{document}

Output

As void-pointer points out, the fonts Cursif, ALS Script, and Ecolier come even closer to the desired output. 

A:

There are several fonts that have cursive Es close to that in the sample. 
Kunstlerscreibsch
http://www.font-db.com/font/kunstlerschreibschjoidbol/38809

Ecolier Court
(SIL license) http://www.fontspace.com/jean-douteau/ecolier

A:

I'd also recommend Detexify!  It allows you to draw a symbol and it shows you possible matches and the TeX required to draw them.  It works very well, I use it all the time!