How do I set the primary boot display on Mac?

How do I set which monitor is used at boot time?

I know I can drag the little menu bar image to whatever monitor I want as my main screen; that's been around for decades. Back in the Mac OS 9 days you could also drag the Happy Mac icon to whatever monitor you wanted the system to use during the boot process, but I can't seem to find how to bring that up now. Did they just never get around to re-implementing that feature when they transitioned to OS 10?