How to query SET undocumented (Hidden) INIT.ora parameters in Oracle?

This post is fairly simple - shows how to query the SET undocumented (Hidden) INIT.ora parameters in your Oracle database.  Each one of these undocumented parameters should only be set with Oracle's consent and approval. The following shows an example query.
SELECT name,description,value from SYS.V$PARAMETER WHERE name LIKE '\_%' ESCAPE '\';
NAME
--------------------------------------------------------------------------------
DESCRIPTION
--------------------------------------------------------------------------------
VALUE
--------------------------------------------------------------------------------
_smu_debug_mode
<debug-flag> - set debug event for testing SMU operations
4
_ignore_desc_in_index
ignore DESC in indexes, sort those columns ascending anyhow
TRUE
_unnest_subquery
enables unnesting of complex subqueries
FALSE
_gby_hash_aggregation_enabled
enable group-by and aggregation using hash scheme
FALSE
_trace_files_public
Create publicly accessible trace files
FALSE