It may be worth pointing out that the rules for when to use long "ſ" and when to use round "s" are not as straightforward as they might appear at first (and these rules vary depending on language and time-period). This is a useful reference: http://babelstone.blogspot.com/2006/06/rules-for-long-s.html
So I'm a bit curious about what algorithm the Day Roman font package uses to automatically choose between "ſ" and "s".
[Edit:]
Following up on Willie Wong's answer above, here's an example using Kepler Project fonts (which works in regular LaTeX):
\documentclass{article}
\usepackage[veryoldstyle]{kpfonts}
\usepackage{graphicx}
\newcommand{\italiclinverted}{\raisebox{.5em}{\rotatebox{180}{\textit{l}}}}
\begin{document}
Where Fractions= are wanting, a Division serves= to distinguish the
Numerator from the Denominator, by putting it thus=; viz.\ 3-8, 12-63,
16-50, though some other symbol might serve better for the purpose; and
therefore we propose one that is= similar to an Italic~\textit{l}
inverted, and whose figure takes= in the whole depth of its= body; which
then would have this= resemblance; viz.\ 3{\italiclinverted}5
12{\italiclinverted}63 16{\italiclinverted}50. And as=
to the thickness= of this= Divider, we think it should not exceed that
of an n-quadrat, but rather join closer to the figures=.
\end{document}
Which looks like