How do we create an historic snapshot i.e. a snapshot at a specific point in time on a stream?

We have a stream on which we forgot to create a snapshot previously and which has now had additional changesets delivered to it. The only way we can see to create an historic snapshot is to create a workspace with the stream as the flow target, accept in just the earlier changesets we require, snapshot the workspace, then change ownership of the snapshot from the workspace to the stream. Is there another simpler way of doing this?