Showing records where groups of 4 are present

Question

I have an example table (input) where I want all records which can be grouped by 4 starting with number 1 (output).
How could I accomplish this?
input:
id     le
1     a
1     b
2     c
1     d
2     d
3     d
1     e
2     e
3     e
4     e
1     f
2     f
3     f
4     f
5     f
1     g
2     g
3     g
4     g
5     g
6     g
1     h
2     h
3     h
4     h
5     h
6     h
7     h
1     I
2     I
3     I
4     I
5     I
6     I
7     I
8     I
9     I
etc..     etc..output:
id     le
1     e
2     e
3     e
4     e
1     f
2     f
3     f
4     f
1     g
2     g
3     g
4     g
1     h
2     h
3     h
4     h
1     I
2     I
3     I
4     I
5     I
6     I
7     I
8     I

Answer 1

Thanks again Rob it works great!
I have used your principe in the real situation and could you give me some advise how I can use less subquueries for the following:
SELECT aliquot_id,external_reference
FROM
     SELECT aliquot_id,external_reference,rn,
            4 * trunc(count(*) over (partition by u_protocol_id)/4) cnt
     FROM
         SELECT aliquot_id,u_box_code, u_protocol_id, external_reference,
                 row_number() over (PARTITION BY u_protocol_id ORDER BY external_reference ASC) rn
         FROM
            SELECT /*+ cardinality (a 100) */ a.aliquot_id,a.external_reference,su.u_box_code, tu.u_protocol_id,
                    mod(row_number() over (PARTITION BY su.u_box_code, tu.u_protocol_id ORDER BY a.external_reference DESC),96) modrn
            FROM lims_sys.sample_user su,lims_sys.aliquot a,lims_sys.test t,lims_sys.test_user tu
            WHERE su.sample_id = a.sample_id
            AND a.aliquot_id = t.aliquot_id
            AND t.test_id = tu.test_id
            AND a.plate_order IS null
           AND a.status IN ('V','P')
          WHERE modrn = 0
WHERE rn <= cnt