Is there API to make humanoid into the default curling pose?

Hi, there.

I want to know if there is an API ( documented or not ) to make the humanoid rigged model into its curling pose?

Here is the reason:

As I'm working on an extension to make skeleton animation in Unity Editor, It works well with Legacy and Generic rigs. But for Humanoid rig, as Unity forbids using Animation Window to make animation with it, I need to workaround using a duplicate Generic rig to make animation with.

However it seems that the Humanoid rig's default pose is not the prefab pose(fig.1), but this (fig.2). It could be solved by adding keyframes at the start of animation, but I want to make a helper function to make adding starting keyframes easier, so I need an api to make the model into the (fig.2) pose.

Fig.1

Fig.2