I'd like my chapters to look like this:

(if it helps, the picture is from the Princeton Lectures in Analysis textbook series by Elias Stein) I know how to insert the quote (using the epigraph package) but I can't find how to style the chapter title like that. I've tried reading the manuals for fncychap and titlesec (I am using the latter already, to make the section titles smaller) but I couldn't understand how to properly use them. Can anyone help me? Thanks!
Here's a MWE so you can make a quick copy-paste to your computer:
\documentclass[12pt,letterpaper]{book}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{titlesec}
\title{MWE}
\author{nelichu}
\begin{document}
\chapter{Measure Theory}
\end{document}
