Partial measure moment

[Gilles]

Hi.

> 
> - Partial bars:
> You probably don't want to use \partial in the middle of a piece. In your 
> example, it tends to destroy the bar numbering. I think it's a better idea to 
> set Timing.measureLength directly.
> 

I found this in the manual:

measurePosition (moment)
    How much of the current measure have we had. This can be set manually to
    create incomplete measures. 


How do I express this "moment" type in a lily file?
I tried

  g2. \set Timing.measurePosition = #1 |

but lilypond complains:

    g2. \set Timing.measurePosition = #1
                                         |
type check for `measurePosition' failed; value `1' must be of type `moment'[24]



Thanks,
Gilles