These Macs do not come with any media for restoring the OS. You boot to the emergency partition by restarting and holding down Command+R. From there you can restore the OS or erase a drive and reinstall. A full install package for Lion or Mountain Lion is 4GB in size. Mavericks and Yosemite are a bit over 5 GB and El Capitan is 6 GB. The entire hidden recovery partition is only 650MB. That tells you right away that this is not an entire system. If you do an erase and install, as much of the OS as is possible will be installed from the recovery partition. The rest will be downloaded from Apple's servers and installed.
I wanted to see what fonts could be restored from the recovery partition. The result is that they are in a hidden .dmg file. In that disk image is a folder named /System/Library/Fonts/Base/. Of the 245 fonts Mountain Lion ships with, only 51 fonts are in this folder. This one folder is actually a combination of fonts which normally go into the /System/Library/Fonts/ folder, and others in the /Library/Fonts/ folder. It's not easy to get to. You need to first modify Disk Utility's preferences so it will show hidden partitions so you can mount the Recovery drive. Then you run a Terminal command to show hidden files and folders. It's not something a novice should attempt, so I'm not going to explain the entire process. There are so few fonts to recover from there anyway it isn't worth the effort.
So whenever you get the opportunity to download an entire Lion, Mountain Lion, Mavericks, Yosemite or El Capitan system through the App Store (as in a system upgrade), do so. When the download finishes, it will want to install the OS. Immediately press Command+Q to quit the installer. You can then backup the full installer to a flash drive or external hard drive. Then you have it and can use the following instructions.
It's quite a bit different as Apple does not sell a CD or DVD for Lion through El Capitan. Lion was available on a flash drive. The following instructions assume you copied your Lion through El Capitan download to an external drive or other location to save for future use. I haven't seen a flash drive version of Lion, so I can't comment on how that may work.
Font locations for Lion, Mountain Lion, Mavericks, Yosemite and El Capitan:
Right click on the Lion, Mountain Lion, Mavericks, Yosemite or El Capitan installer and choose Show Package Contents. Double click the Contents folder, and then the SharedSupport folder. Double click the file InstallESD.dmg to open the disk image. A disk image drive icon will appear on the desktop. Double click the desktop icon to open it. In the resulting window, double click the Packages folder. Open the Essentials.pkg with Pacifist. You can do this by dragging and dropping the .pkg file onto Pacifist's interface.
For the System folder fonts, expand Contents of Essentials.pkg > System > Library > Fonts and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
For the Library folder fonts, expand Contents of Essentials.pkg > Library > Fonts and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
Font locations for the Leopard and Snow Leopard retail disks:
For the System folder fonts, expand Contents of OSInstall.mpkg > Contents of EssentialSystemSoftware > Contents of
EssentialSystemSoftwareGroup > Contents of BaseSystem.pkg > System > Library > Fonts and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
For the Library folder fonts, expand Contents of OSInstall.mpkg > Contents of EssentialSystemSoftware > Contents of
EssentialSystemSoftwareGroup > Contents of Essentials.pkg > Library > Fonts and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
The Additional Fonts are in two separate locations. Expand Contents of OSInstall.mpkg > Contents of AdditionalFonts.pkg > Library > Fonts, or Contents of OSInstall.mpkg > Contents of AdditionalFonts.pkg > System > Library > Fonts, depending on the set of additional fonts you want to restore.
Font locations for the Tiger retail disks:
For the System folder fonts, expand Contents of OSInstall.mpkg > Contents of BaseSystem.pkg > System > Library and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
For the Library folder fonts, expand Contents of OSInstall.mpkg > Contents of Essentials.pkg > Library and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
Fonts locations for the bundled Tiger and retail Panther disks:
For the System folder fonts, expand Contents of OSInstall.mpkg > Contents of EssentialSystemSoftware.mpkg > Contents of
BaseSystem.pkg > System > Library and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
For the Library folder fonts, expand Contents of OSInstall.mpkg > Contents of EssentialSystemSoftware.mpkg > Contents of Essentials.pkg > Library and highlight the folder "Fonts" by clicking on it once. Click "Install" at the upper left of the Pacifist window.
You will also find a main package named Contents of Fonts.mpkg. You do not need to restore these fonts unless you have need of the extended set of Asian and foreign language fonts. Also, you can expand each "Fonts" folder in Pacifist to select individual fonts if you only want to restore one, or a few.