Although it might seem strange to emulate an Apple on an Apple, it isn't. Everybody does it when using Classic under OS X. VMac and Basilisk can be used to emulate older Macs (System 6). To emulate an Apple IIe one can use OSXII. Finally, it is possible to emulate the first Apple, the Apple I, with Cocoa Pom.

Apple OS7.5 is freely available from here

Cocoa Pom
OSXII
Vmac
Basilisk