I can risk 25% of my emergency fund account in VTI. So I just setup a few buy limit orders to execute in my Vanguard Brokerage Account, a little over $1000 of buy limit orders currently. This would pick up VTI at discounts. If the orders don't execute it's no problem because I am still getting 4.55% return via money market. Just thought I'd share my idea. (I've shared this idea before here with mixed reactions, but this time it's in an account earning me near 5% interest, not 0%.)
It's still an emergency fund, I mean I can sell VTI if I have to after I've used up 75% of the cash emergency fund in this account.
EDIT: Currently I have no VTI in my emergency fund, it's all cash. Ultimately my emergency fund will be about $50k.