Size of individual transactions in log file
Please refer following link to get answer to your question :

To get the size of each open transactions refer following link

https://www.mssqltips.com/sqlservertip/1225/how-to-determine-sql-server-database-transaction-log-usage/

If you want to know the transaction log of any historical date then you can take the backup of database or just a transaction log backup and use third party tools to read those logs. It will also allows you to read the the logs taken by date.(ApexSQL Log tool, SQL Log Rescue)

Hope this helps.