Fonts & Character Sets ⇒ Give me my fancy math X from mathptmx back!

[user49915]

In the old times of mathptmx, we wrote stuff such as

\documentclass{article}
\pagestyle{empty}
\usepackage{mathptmx}
\begin{document}
Let \(\mathcal{X}=\{X_1,\ldots,X_n\}\).
\end{document}

and got from pdflatex a fancy calligraphic math X, which was sufficiently fancy to be visibly distinct from the remaining italicized X in X_1 till X_n:

mwe1.png (5.3 KiB) Viewed 8013 times

However, in the more modern times, mathptmx has been obsoleted in favor of newtx.
Feeding

\documentclass{article}
\pagestyle{empty}
\usepackage{newtxmath}
\begin{document}
Let \(\mathcal{X}=\{X_1,\ldots,X_n\}\).
\end{document}

to pdflatex results in a dull

mwe2.png (4.86 KiB) Viewed 8013 times

The distinction between the first X and the remaining occurrences is far less prominent. This is unfortunate, as it requires additional attention from the reader to distinguish between the two.

For pdflatex, what is the advised way of getting the fancy math X, such as in mathptmx, , or similar, if you use newtxtext and newtxmath for standard text and math fonts? Yes, I know there is mathrsfs, which is not obsolete in CTAN but is pretty dated (1999-06-30 is the date of the file http://mirrors.ctan.org/macros/latex/co ... thrsfs.sty on the CTAN file system and 1996-01-01 is the internal date stated inside http://mirrors.ctan.org/macros/latex/co ... thrsfs.sty). Is it still advisable to use mathrsfs+\mathscr or are there better options?

Crosspost: http://tex.stackexchange.com/questions/536297

[Johannes_B]

You know you could just input a picture of your letter.

[user49915]

A picture of X wouldn't result in X in the text layer of the PDF file generated. Moreover, I find it difficult to size-scale it automatically if needed.

[samcarter]

It is trivial to size scale it automatically if one uses a unit relative to the font size, e.g. em

[user49915]

It is trivial to size scale it automatically if one uses a unit relative to the font size, e.g. em

I correct myself: I find it difficult... Probably, you mean ex rather than em, to match the height of the font.
Anyway, even if it's solved, the problem of how to get X into the PDF text layer remains.