Can i get my horse into a boat?

Since 1.9, boats can supposedly transport two entities... I can not for the life of me get my horse into the boat.

Can it be done? If yes how? What about a donkey? If not, which animals can be transported, which can not?

You can get both inside.

1. Find/breed a baby horse/donkey

2. Push it into the boat

3. Stuff it with apples to grow

4. Tame it

5. Put a chest and/or a saddle on it

6. Enjoy your ride!

I recommend you use a lead to tie your horse and ride the boat like in this picture:

Don't worry about the lead, as long as you are in the boat.

I don't want to give out misinformation as I don't have any proof that Mojang intentionally removed mobs entering boats, so I've removed the update section of this answer.

Additional proof that this is, in fact, replicable in 1.16+