Before moving any data, clearly define what data you need to transfer from PostHog to MySQL. Identify the specific tables, events, or user properties that are relevant for your analysis or reporting requirements.

PostHog provides an API to access the data programmatically. To use it, you'll need to generate an API key from the PostHog interface. Go to your PostHog account, navigate to the settings, and create an API key. This key will be used to authenticate your requests.

Write a script in a programming language such as Python to call the PostHog API endpoints and retrieve the data. Use the `requests` library to make GET requests to the relevant API endpoints like `/api/events/` or `/api/people/`. Make sure to handle pagination if there’s a large volume of data.

```python
import requests

api_key = 'YOUR_POSTHOG_API_KEY'
headers = {
'Authorization': f'Bearer {api_key}',
'Content-Type': 'application/json',
}
response = requests.get('https://app.posthog.com/api/events/', headers=headers)
data = response.json()
```

Once you have the data in a JSON or similar format, transform it into a structure suitable for MySQL. This might involve converting timestamps to MySQL datetime format, flattening nested JSON objects, or translating field names to match your MySQL schema.

Prepare your MySQL database by creating tables that will store the data extracted from PostHog. Use the MySQL command line or a GUI tool like MySQL Workbench to create tables with columns that match the transformed data structure.

```sql
CREATE TABLE events (
id INT AUTO_INCREMENT PRIMARY KEY,
event_name VARCHAR(255),
event_time DATETIME,
properties JSON
);
```

Write a script to insert the transformed data into your MySQL database. Use a library like `mysql-connector-python` to connect to your MySQL instance and execute `INSERT` statements to populate your tables.

```python
import mysql.connector

cnx = mysql.connector.connect(user='username', password='password', host='127.0.0.1', database='your_database')
cursor = cnx.cursor()

add_event = ("INSERT INTO events "
"(event_name, event_time, properties) "
"VALUES (%s, %s, %s)")

for event in data['results']:
event_data = (event['event'], event['timestamp'], json.dumps(event['properties']))
cursor.execute(add_event, event_data)

cnx.commit()
cursor.close()
cnx.close()
```

After loading the data, ensure that the data transfer was successful and that all records in your MySQL database match what was in PostHog. This can be done by running queries to check record counts, data completeness, and spot-checking sample records for accuracy.

By following these steps, you can manually transfer data from PostHog to a MySQL destination without relying on third-party connectors or integrations.