The df command will show you how much space is available. I have about 10MB free in "/", so a 15MB font won't fit.
I have found fonts very frustrating on the iLiad. According to the ~/.fonts.config file it should be possible to add fonts in a "fonts" directory on the CF card (/media/cf/fonts). However, this has not worked for me, even though a fonts.cache-1 file is created (as expected). The new fonts do not show up in FBReader, for example. I also tried ~/.fonts (which I think is the right place, i.e. /home/root/.fonts, not /root/.font) without success.
From a desktop computer, you can create a fonts directory and put .ttf files in it on any USB connected iLiad filesystem. As I said above, this did not work for me - but it may be worth trying (because these filesystems are larger). If you want to try a smallish font file on the root filesystem, use mrxvt and something like:
Code:
mkdir /home/root/.fonts
cd /media/cf
ls *.ttf
cp *.ttf /home/root/.fonts
ls /home/root/.fonts
If you use version 0.4 of mrxvt, the "home" key will exit mrxvt. Note that "~" can be used in place of /home/root (e.g. ~/.fonts). Once you add a new font, a reboot should be all you need to use it.